<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:6f8152f1-4e4e-430b-a463-d987c0feb634,g:4c0f1eaa-37dc-4519-a72b-3372510657c7-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.cmegroup.com/role/Cover" xlink:type="simple" xlink:href="cme-20250930.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_233acfca-864f-4e7d-8fe3-24a967fca651" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_us-gaap_StatementTable_233acfca-864f-4e7d-8fe3-24a967fca651" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_9386bf02-d126-4203-8e6d-af7c862b9961" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_233acfca-864f-4e7d-8fe3-24a967fca651" xlink:to="loc_us-gaap_StatementClassOfStockAxis_9386bf02-d126-4203-8e6d-af7c862b9961" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9386bf02-d126-4203-8e6d-af7c862b9961_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9386bf02-d126-4203-8e6d-af7c862b9961" xlink:to="loc_us-gaap_ClassOfStockDomain_9386bf02-d126-4203-8e6d-af7c862b9961_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_bbcbd69f-dc03-4133-999e-333c4584ab67" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9386bf02-d126-4203-8e6d-af7c862b9961" xlink:to="loc_us-gaap_ClassOfStockDomain_bbcbd69f-dc03-4133-999e-333c4584ab67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_6bd20cb9-6121-49cb-94e0-999bc314a6e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_bbcbd69f-dc03-4133-999e-333c4584ab67" xlink:to="loc_us-gaap_CommonClassAMember_6bd20cb9-6121-49cb-94e0-999bc314a6e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ClassBCommonStockClassB1Member_b01c5766-d2a5-427d-aca7-9da76b94a652" xlink:href="cme-20250930.xsd#cme_ClassBCommonStockClassB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_bbcbd69f-dc03-4133-999e-333c4584ab67" xlink:to="loc_cme_ClassBCommonStockClassB1Member_b01c5766-d2a5-427d-aca7-9da76b94a652" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ClassBCommonStockClassB2Member_8dfdd3f3-56d9-4ae8-a01f-56433c76f4a8" xlink:href="cme-20250930.xsd#cme_ClassBCommonStockClassB2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_bbcbd69f-dc03-4133-999e-333c4584ab67" xlink:to="loc_cme_ClassBCommonStockClassB2Member_8dfdd3f3-56d9-4ae8-a01f-56433c76f4a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ClassBCommonStockClassB3Member_17a71c73-69be-4730-b359-dd1845cd0ae3" xlink:href="cme-20250930.xsd#cme_ClassBCommonStockClassB3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_bbcbd69f-dc03-4133-999e-333c4584ab67" xlink:to="loc_cme_ClassBCommonStockClassB3Member_17a71c73-69be-4730-b359-dd1845cd0ae3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ClassBCommonStockClassB4Member_8efec798-6fe7-41b1-99d5-08efbda591b3" xlink:href="cme-20250930.xsd#cme_ClassBCommonStockClassB4Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_bbcbd69f-dc03-4133-999e-333c4584ab67" xlink:to="loc_cme_ClassBCommonStockClassB4Member_8efec798-6fe7-41b1-99d5-08efbda591b3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_b662d9a1-ecdf-4dfe-8807-cb0ba14cf2a0" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_DocumentType_b662d9a1-ecdf-4dfe-8807-cb0ba14cf2a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_885a6c73-8f04-4f3d-a65d-b7eeb72f4443" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_DocumentQuarterlyReport_885a6c73-8f04-4f3d-a65d-b7eeb72f4443" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_cd43586f-5196-436e-8a61-10053bd7fa0c" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_DocumentPeriodEndDate_cd43586f-5196-436e-8a61-10053bd7fa0c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_f0d44721-af7f-4964-8446-93dd9b2ef2de" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_DocumentTransitionReport_f0d44721-af7f-4964-8446-93dd9b2ef2de" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_19901a21-1919-47cd-ae44-3f7a263c6708" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityFileNumber_19901a21-1919-47cd-ae44-3f7a263c6708" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_2078668f-4810-457b-9482-c94351359925" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityRegistrantName_2078668f-4810-457b-9482-c94351359925" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_fd64bb2a-e08e-44b8-bf99-080a90db2b43" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityIncorporationStateCountryCode_fd64bb2a-e08e-44b8-bf99-080a90db2b43" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_4972d188-b2a4-4213-8e2f-8225d467e085" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityTaxIdentificationNumber_4972d188-b2a4-4213-8e2f-8225d467e085" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_df3fd20f-e4b0-4ab4-96c6-bd83463c7704" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityAddressAddressLine1_df3fd20f-e4b0-4ab4-96c6-bd83463c7704" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_1ccb4cc4-579a-41a5-90c2-eb599d1f30e1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityAddressCityOrTown_1ccb4cc4-579a-41a5-90c2-eb599d1f30e1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_9802d846-4528-4622-bc84-c679e72ddfd4" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityAddressStateOrProvince_9802d846-4528-4622-bc84-c679e72ddfd4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_e872fb50-1262-4820-a851-bd4cc639463c" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityAddressPostalZipCode_e872fb50-1262-4820-a851-bd4cc639463c" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_85968232-a356-4bd7-9d14-070b46051c4d" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_CityAreaCode_85968232-a356-4bd7-9d14-070b46051c4d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_622cdb16-e631-4365-b34a-b5308eb97fc5" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_LocalPhoneNumber_622cdb16-e631-4365-b34a-b5308eb97fc5" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_0cb27e73-7a62-4aba-8e3c-6518b3112b58" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityCurrentReportingStatus_0cb27e73-7a62-4aba-8e3c-6518b3112b58" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_f6cdc83b-a17d-4d59-87ae-e0fb692fef07" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityInteractiveDataCurrent_f6cdc83b-a17d-4d59-87ae-e0fb692fef07" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_d7fd702b-5323-4841-ab47-1004bc0e2435" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityFilerCategory_d7fd702b-5323-4841-ab47-1004bc0e2435" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_06a8459a-2c8f-4f82-8ebf-8de040d5f089" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntitySmallBusiness_06a8459a-2c8f-4f82-8ebf-8de040d5f089" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_1bc36dba-f1ed-448b-9211-d1a551dd7888" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityEmergingGrowthCompany_1bc36dba-f1ed-448b-9211-d1a551dd7888" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_4aaad849-211d-445e-adbe-9e9887ab95a3" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityShellCompany_4aaad849-211d-445e-adbe-9e9887ab95a3" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_833e2a7d-cae7-4a05-96d2-94f033e7154d" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_833e2a7d-cae7-4a05-96d2-94f033e7154d" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_60cf6685-5bb7-4d13-95e7-487cfcd7ffc4" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_Security12bTitle_60cf6685-5bb7-4d13-95e7-487cfcd7ffc4" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_f35493e9-51e5-4782-8211-a2695b056a15" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_TradingSymbol_f35493e9-51e5-4782-8211-a2695b056a15" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_f52508b2-7fd0-4ead-b4bb-5afe41a753d1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_SecurityExchangeName_f52508b2-7fd0-4ead-b4bb-5afe41a753d1" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_f13e0dbb-3c84-43ca-80a4-7289663ac6b1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_DocumentFiscalPeriodFocus_f13e0dbb-3c84-43ca-80a4-7289663ac6b1" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_2bf9e10a-6304-46be-875a-08ee5f5d98e8" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_DocumentFiscalYearFocus_2bf9e10a-6304-46be-875a-08ee5f5d98e8" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_187e0274-c1fa-463d-bf4e-a4995cb84ea1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_CurrentFiscalYearEndDate_187e0274-c1fa-463d-bf4e-a4995cb84ea1" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_4d150fe4-f202-4a31-b062-7861f8608225" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_EntityCentralIndexKey_4d150fe4-f202-4a31-b062-7861f8608225" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_6316f9e6-6c0c-497d-ab9f-357f7ebc1e56" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f9d165b3-81ce-4b5c-a88c-c800f6567701" xlink:to="loc_dei_AmendmentFlag_6316f9e6-6c0c-497d-ab9f-357f7ebc1e56" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="cme-20250930.xsd#ConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_8f44de4a-62ae-4229-b62b-65afc3a243a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6853a48c-4572-4332-9d2b-f972312f5b8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_8f44de4a-62ae-4229-b62b-65afc3a243a5" xlink:to="loc_us-gaap_StatementTable_6853a48c-4572-4332-9d2b-f972312f5b8c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_2f4afe8d-a1a2-4413-9d72-795cc5d3355f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6853a48c-4572-4332-9d2b-f972312f5b8c" xlink:to="loc_us-gaap_StatementClassOfStockAxis_2f4afe8d-a1a2-4413-9d72-795cc5d3355f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_2f4afe8d-a1a2-4413-9d72-795cc5d3355f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_2f4afe8d-a1a2-4413-9d72-795cc5d3355f" xlink:to="loc_us-gaap_ClassOfStockDomain_2f4afe8d-a1a2-4413-9d72-795cc5d3355f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_af0df5f2-97a4-4e77-8794-15bafbbb361c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_2f4afe8d-a1a2-4413-9d72-795cc5d3355f" xlink:to="loc_us-gaap_ClassOfStockDomain_af0df5f2-97a4-4e77-8794-15bafbbb361c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_2d4a9c35-c386-4a1d-aa6c-c34cb9f56b32" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_af0df5f2-97a4-4e77-8794-15bafbbb361c" xlink:to="loc_us-gaap_CommonClassAMember_2d4a9c35-c386-4a1d-aa6c-c34cb9f56b32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_6ed2b2aa-c0a4-433a-96af-11e1cbc8c7fc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_af0df5f2-97a4-4e77-8794-15bafbbb361c" xlink:to="loc_us-gaap_CommonClassBMember_6ed2b2aa-c0a4-433a-96af-11e1cbc8c7fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8f44de4a-62ae-4229-b62b-65afc3a243a5" xlink:to="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d72f7595-6211-4c03-9a68-96df4dcff50a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d72f7595-6211-4c03-9a68-96df4dcff50a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesCurrent_5b467d3c-9c6c-4ce9-9922-f8089b129131" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MarketableSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_MarketableSecuritiesCurrent_5b467d3c-9c6c-4ce9-9922-f8089b129131" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_94cca473-1139-42ce-992b-f1d875a3168d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_94cca473-1139-42ce-992b-f1d875a3168d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_5b37e428-5a22-4b9d-9e98-855b73bceb90" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_OtherAssetsCurrent_5b37e428-5a22-4b9d-9e98-855b73bceb90" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodFaithAndMarginDepositsWithBrokerDealers_3b08a206-8100-48f7-9dbb-9896ec42a868" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodFaithAndMarginDepositsWithBrokerDealers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_GoodFaithAndMarginDepositsWithBrokerDealers_3b08a206-8100-48f7-9dbb-9896ec42a868" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_2d63a7e8-b951-4bda-8a3d-3e22569e5624" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_AssetsCurrent_2d63a7e8-b951-4bda-8a3d-3e22569e5624" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_41c80e71-c94a-4378-b6da-0d0d3d1bc5f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_41c80e71-c94a-4378-b6da-0d0d3d1bc5f3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_Intangibleassetstradingproducts_b4bd6165-2f49-4a3a-ab3b-612c74424a1c" xlink:href="cme-20250930.xsd#cme_Intangibleassetstradingproducts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_cme_Intangibleassetstradingproducts_b4bd6165-2f49-4a3a-ab3b-612c74424a1c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_9afef915-25ce-4ab8-b0db-0343cd0f59a9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_9afef915-25ce-4ab8-b0db-0343cd0f59a9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_67818c24-c701-47c2-9bb6-c2c4532f88dc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_Goodwill_67818c24-c701-47c2-9bb6-c2c4532f88dc" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_c73dd58f-8014-44b7-ac99-6dca0bf182a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_c73dd58f-8014-44b7-ac99-6dca0bf182a6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_33c4f4f7-c0ad-489d-8805-4241ea9dd4f5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_5f4df1d4-7277-47ca-93b8-31b91893f3a7" xlink:to="loc_us-gaap_Assets_33c4f4f7-c0ad-489d-8805-4241ea9dd4f5" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8f44de4a-62ae-4229-b62b-65afc3a243a5" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_6cf05aff-3cae-4f81-832f-fef0acda05b0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_AccountsPayableCurrent_6cf05aff-3cae-4f81-832f-fef0acda05b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_b16734df-4828-4603-bd62-d92470dc76b6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_ShortTermBorrowings_b16734df-4828-4603-bd62-d92470dc76b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_1089692c-3953-4809-a70e-513912caa507" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_1089692c-3953-4809-a70e-513912caa507" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_MarginDepositsAndGuarantyFundsLiabilitiesCurrent_1ceb62d1-ac6b-4560-b2f0-4b9a59326fca" xlink:href="cme-20250930.xsd#cme_MarginDepositsAndGuarantyFundsLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_cme_MarginDepositsAndGuarantyFundsLiabilitiesCurrent_1ceb62d1-ac6b-4560-b2f0-4b9a59326fca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_2e1c65c6-4faa-4e13-b93e-80cf86f7619a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_LiabilitiesCurrent_2e1c65c6-4faa-4e13-b93e-80cf86f7619a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredLongTermDebt_ce161e26-fbe8-4fd6-9006-9a2d1fb3a5e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnsecuredLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_UnsecuredLongTermDebt_ce161e26-fbe8-4fd6-9006-9a2d1fb3a5e2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_4659aca2-8e97-4fec-814f-8b1b7da07fdc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_4659aca2-8e97-4fec-814f-8b1b7da07fdc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_3a8152c1-f26b-44da-bd86-4b6e1a28b5f5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_3a8152c1-f26b-44da-bd86-4b6e1a28b5f5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_d6e44d62-0b12-4b68-9cfb-16a36bc331c2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_Liabilities_d6e44d62-0b12-4b68-9cfb-16a36bc331c2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_3627f010-2aa2-4236-aa7f-002cc861a1da" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:to="loc_us-gaap_PreferredStockValue_3627f010-2aa2-4236-aa7f-002cc861a1da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValueOutstanding_b3d2fb67-62f7-4940-8124-34ee2a0941f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockValueOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:to="loc_us-gaap_CommonStockValueOutstanding_b3d2fb67-62f7-4940-8124-34ee2a0941f6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_073c3fe3-c9c7-4da1-8900-11ec68cfb30b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_073c3fe3-c9c7-4da1-8900-11ec68cfb30b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_d353863e-f32e-4392-897a-12f75f652237" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_d353863e-f32e-4392-897a-12f75f652237" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_87f79af9-edef-47d0-bd62-3ec3c4b5db66" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_87f79af9-edef-47d0-bd62-3ec3c4b5db66" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_0d721c42-0154-4ec0-8cdc-499a178c4f08" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_026c2bde-7882-4506-b30b-ff8def39c210" xlink:to="loc_us-gaap_StockholdersEquity_0d721c42-0154-4ec0-8cdc-499a178c4f08" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_3e1537f3-95c8-4133-88ba-06fd18fa75a7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_f1fb3ce1-ec1f-45fb-96b5-791e9218c8a5" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_3e1537f3-95c8-4133-88ba-06fd18fa75a7" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="cme-20250930.xsd#ConsolidatedBalanceSheetsParenthetical"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_b1185bad-7aad-4ee9-8dcb-f6101c2a9774" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_StatementTable_b1185bad-7aad-4ee9-8dcb-f6101c2a9774" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_4843ab67-6b83-4900-8da7-8263e117431c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_b1185bad-7aad-4ee9-8dcb-f6101c2a9774" xlink:to="loc_us-gaap_StatementClassOfStockAxis_4843ab67-6b83-4900-8da7-8263e117431c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4843ab67-6b83-4900-8da7-8263e117431c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4843ab67-6b83-4900-8da7-8263e117431c" xlink:to="loc_us-gaap_ClassOfStockDomain_4843ab67-6b83-4900-8da7-8263e117431c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a7647dc9-bb74-4abe-be85-0771383265f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4843ab67-6b83-4900-8da7-8263e117431c" xlink:to="loc_us-gaap_ClassOfStockDomain_a7647dc9-bb74-4abe-be85-0771383265f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_4e3d3d92-c018-4252-82a6-13c06546eb89" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a7647dc9-bb74-4abe-be85-0771383265f2" xlink:to="loc_us-gaap_PreferredStockMember_4e3d3d92-c018-4252-82a6-13c06546eb89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_d4eba900-2e57-4d86-b77a-0044fbb31fa7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a7647dc9-bb74-4abe-be85-0771383265f2" xlink:to="loc_us-gaap_CommonClassAMember_d4eba900-2e57-4d86-b77a-0044fbb31fa7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_cdb7a772-8109-4035-91fd-8c5e2aceb4fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a7647dc9-bb74-4abe-be85-0771383265f2" xlink:to="loc_us-gaap_CommonClassBMember_cdb7a772-8109-4035-91fd-8c5e2aceb4fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_71466c98-9cfb-4f82-a26f-940cd5a00521" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_71466c98-9cfb-4f82-a26f-940cd5a00521" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_07ccb9bd-4fb4-4763-ad80-e90b812cbe94" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_07ccb9bd-4fb4-4763-ad80-e90b812cbe94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_4f9a530d-8523-4634-89a5-d9ee103a95d3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_4f9a530d-8523-4634-89a5-d9ee103a95d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_8a7a7462-00db-4685-9b6c-846de0c1aec5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_8a7a7462-00db-4685-9b6c-846de0c1aec5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_9755ffb9-ae1b-4933-aabe-d7ddc476f6bd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_9755ffb9-ae1b-4933-aabe-d7ddc476f6bd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_d58447c2-f5f5-4b80-a613-297a8062fb80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_d58447c2-f5f5-4b80-a613-297a8062fb80" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_e31bb5c4-a0d8-4400-9c3b-a1be7f539860" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_PreferredStockSharesIssued_e31bb5c4-a0d8-4400-9c3b-a1be7f539860" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_f0e55643-317d-4484-a5f0-a98c99cae3d8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_f0e55643-317d-4484-a5f0-a98c99cae3d8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_7144d964-8ef2-4be2-852f-67470c5fb0cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_7144d964-8ef2-4be2-852f-67470c5fb0cd" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_4e4bfc17-0669-4e72-891d-3e61989558ba" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_4e4bfc17-0669-4e72-891d-3e61989558ba" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_e40e0132-d938-494b-9fef-d79c5f6e7bb3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_CommonStockSharesIssued_e40e0132-d938-494b-9fef-d79c5f6e7bb3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_f38c9c1e-2ad1-4eb8-9e27-9108bda942c4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1144c788-ed0d-491b-9f29-f35205f2bbf8" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_f38c9c1e-2ad1-4eb8-9e27-9108bda942c4" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/ConsolidatedStatementsOfIncome" xlink:type="simple" xlink:href="cme-20250930.xsd#ConsolidatedStatementsOfIncome"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/ConsolidatedStatementsOfIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_1ca6e1f4-ef54-46f1-ac87-3225e2cf4b23" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_StatementTable_1ca6e1f4-ef54-46f1-ac87-3225e2cf4b23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_4b25c7bc-f934-45a2-abc5-7577f1ce2ea7" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1ca6e1f4-ef54-46f1-ac87-3225e2cf4b23" xlink:to="loc_srt_ProductOrServiceAxis_4b25c7bc-f934-45a2-abc5-7577f1ce2ea7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4b25c7bc-f934-45a2-abc5-7577f1ce2ea7_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_4b25c7bc-f934-45a2-abc5-7577f1ce2ea7" xlink:to="loc_srt_ProductsAndServicesDomain_4b25c7bc-f934-45a2-abc5-7577f1ce2ea7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4f017b0a-240f-4e04-bfc2-cc0752ea4db1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_4b25c7bc-f934-45a2-abc5-7577f1ce2ea7" xlink:to="loc_srt_ProductsAndServicesDomain_4f017b0a-240f-4e04-bfc2-cc0752ea4db1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ClearingandtransactionfeesMember_2e6c9563-e177-4cdd-8202-e0fd59326d2e" xlink:href="cme-20250930.xsd#cme_ClearingandtransactionfeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4f017b0a-240f-4e04-bfc2-cc0752ea4db1" xlink:to="loc_cme_ClearingandtransactionfeesMember_2e6c9563-e177-4cdd-8202-e0fd59326d2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_MarketDataMember_41035187-3a47-4738-bfca-3755113c92b2" xlink:href="cme-20250930.xsd#cme_MarketDataMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4f017b0a-240f-4e04-bfc2-cc0752ea4db1" xlink:to="loc_cme_MarketDataMember_41035187-3a47-4738-bfca-3755113c92b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_OtherRevenueMember_563625e6-0c79-4e7b-aea3-9611dced0bd4" xlink:href="cme-20250930.xsd#cme_OtherRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4f017b0a-240f-4e04-bfc2-cc0752ea4db1" xlink:to="loc_cme_OtherRevenueMember_563625e6-0c79-4e7b-aea3-9611dced0bd4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_77975059-3ed9-490a-9fad-97ba5ea99e8a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_RevenuesAbstract_77975059-3ed9-490a-9fad-97ba5ea99e8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_0b925604-6541-498c-9360-189f75e2708a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_77975059-3ed9-490a-9fad-97ba5ea99e8a" xlink:to="loc_us-gaap_Revenues_0b925604-6541-498c-9360-189f75e2708a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_36a1fb14-2f24-4e2c-8b1d-12cd60e45227" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_us-gaap_LaborAndRelatedExpense_36a1fb14-2f24-4e2c-8b1d-12cd60e45227" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InformationTechnologyAndDataProcessing_4b4bc59f-5077-4663-92d1-7ef5f44fcfc5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InformationTechnologyAndDataProcessing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_us-gaap_InformationTechnologyAndDataProcessing_4b4bc59f-5077-4663-92d1-7ef5f44fcfc5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_777264f0-e1d4-4776-ac9a-a6296a16fafc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_us-gaap_ProfessionalFees_777264f0-e1d4-4776-ac9a-a6296a16fafc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_1289890d-ecd4-4286-8013-2898d7a65fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_1289890d-ecd4-4286-8013-2898d7a65fdd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_8cf8937d-d977-48e2-8ad1-7c8123b37465" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_us-gaap_Depreciation_8cf8937d-d977-48e2-8ad1-7c8123b37465" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_LicensingFees_853e863f-0c1c-44c2-97d6-5cc74f7bb981" xlink:href="cme-20250930.xsd#cme_LicensingFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_cme_LicensingFees_853e863f-0c1c-44c2-97d6-5cc74f7bb981" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_bef4da32-eceb-4aa9-8f62-836282e87a10" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_bef4da32-eceb-4aa9-8f62-836282e87a10" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_0d66651f-6f3e-462d-8ce1-21b2e4fc3026" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_0b37a291-f942-4150-ab5f-00a6383bd90c" xlink:to="loc_us-gaap_CostsAndExpenses_0d66651f-6f3e-462d-8ce1-21b2e4fc3026" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_65ef99e1-c866-45c9-9181-1554c327c83a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_OperatingIncomeLoss_65ef99e1-c866-45c9-9181-1554c327c83a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_2f1392f4-fb88-4569-ad48-151847aab730" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_2f1392f4-fb88-4569-ad48-151847aab730" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeNonoperating_b7938df4-ce2b-4149-b605-ee820e3ed9f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentIncomeNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_2f1392f4-fb88-4569-ad48-151847aab730" xlink:to="loc_us-gaap_InvestmentIncomeNonoperating_b7938df4-ce2b-4149-b605-ee820e3ed9f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndDebtExpense_497be1bc-a6fb-4422-9673-a41ba595127d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestAndDebtExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_2f1392f4-fb88-4569-ad48-151847aab730" xlink:to="loc_us-gaap_InterestAndDebtExpense_497be1bc-a6fb-4422-9673-a41ba595127d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_da2e81b9-5b60-46f7-bc7e-bf0f296714c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_2f1392f4-fb88-4569-ad48-151847aab730" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_da2e81b9-5b60-46f7-bc7e-bf0f296714c7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_85d6a794-ab13-4d09-8b1c-0389fa742fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_2f1392f4-fb88-4569-ad48-151847aab730" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_85d6a794-ab13-4d09-8b1c-0389fa742fdd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_1d17ad38-64ff-450f-b676-fb3099dbf0fa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_2f1392f4-fb88-4569-ad48-151847aab730" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_1d17ad38-64ff-450f-b676-fb3099dbf0fa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_e2d93862-fe26-49b4-abac-253717adc60c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_e2d93862-fe26-49b4-abac-253717adc60c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_89663b71-2d4b-4f10-9a98-7fc08111fe68" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_89663b71-2d4b-4f10-9a98-7fc08111fe68" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_e140f5eb-d060-4354-bc90-39a3c6ddd424" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_e140f5eb-d060-4354-bc90-39a3c6ddd424" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_e160b425-82c7-4b83-9c58-a39a6377b366" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_da834f29-33f4-474d-9522-608014cb3388" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_e160b425-82c7-4b83-9c58-a39a6377b366" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/ConsolidatedStatementsOfShareholdersEquity" xlink:type="simple" xlink:href="cme-20250930.xsd#ConsolidatedStatementsOfShareholdersEquity"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/ConsolidatedStatementsOfShareholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_a8da8855-57ad-4719-87b5-9ca69333a62a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StatementTable_a8da8855-57ad-4719-87b5-9ca69333a62a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_175ddf38-a9f1-4572-9697-5f0593ee2798" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_a8da8855-57ad-4719-87b5-9ca69333a62a" xlink:to="loc_us-gaap_StatementClassOfStockAxis_175ddf38-a9f1-4572-9697-5f0593ee2798" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_175ddf38-a9f1-4572-9697-5f0593ee2798_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_175ddf38-a9f1-4572-9697-5f0593ee2798" xlink:to="loc_us-gaap_ClassOfStockDomain_175ddf38-a9f1-4572-9697-5f0593ee2798_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4c0e3941-6832-4c4c-b9a6-81264ab76aa6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_175ddf38-a9f1-4572-9697-5f0593ee2798" xlink:to="loc_us-gaap_ClassOfStockDomain_4c0e3941-6832-4c4c-b9a6-81264ab76aa6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_1164de7d-b45b-49c9-8e32-60cff652000e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_4c0e3941-6832-4c4c-b9a6-81264ab76aa6" xlink:to="loc_us-gaap_CommonClassAMember_1164de7d-b45b-49c9-8e32-60cff652000e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_09b27fd2-2775-48e2-81c6-1155f7daa5cb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_4c0e3941-6832-4c4c-b9a6-81264ab76aa6" xlink:to="loc_us-gaap_CommonClassBMember_09b27fd2-2775-48e2-81c6-1155f7daa5cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_de4c3101-9048-4ee0-83a9-b9a429868eb0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_4c0e3941-6832-4c4c-b9a6-81264ab76aa6" xlink:to="loc_us-gaap_PreferredStockMember_de4c3101-9048-4ee0-83a9-b9a429868eb0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_febb45d8-7cfa-43ba-a3a6-3503c86c9fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_a8da8855-57ad-4719-87b5-9ca69333a62a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_febb45d8-7cfa-43ba-a3a6-3503c86c9fdd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_febb45d8-7cfa-43ba-a3a6-3503c86c9fdd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_febb45d8-7cfa-43ba-a3a6-3503c86c9fdd" xlink:to="loc_us-gaap_EquityComponentDomain_febb45d8-7cfa-43ba-a3a6-3503c86c9fdd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6f3d1eac-fac6-4c74-9e46-78c3b41a683f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_febb45d8-7cfa-43ba-a3a6-3503c86c9fdd" xlink:to="loc_us-gaap_EquityComponentDomain_6f3d1eac-fac6-4c74-9e46-78c3b41a683f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockIncludingAdditionalPaidInCapitalMember_1ff2404e-e55d-48e5-97ef-a1675ff60ff0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockIncludingAdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6f3d1eac-fac6-4c74-9e46-78c3b41a683f" xlink:to="loc_us-gaap_CommonStockIncludingAdditionalPaidInCapitalMember_1ff2404e-e55d-48e5-97ef-a1675ff60ff0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_a1748044-3724-4ef7-a54b-ac8a862ee2bc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6f3d1eac-fac6-4c74-9e46-78c3b41a683f" xlink:to="loc_us-gaap_RetainedEarningsMember_a1748044-3724-4ef7-a54b-ac8a862ee2bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_d696dc1e-b171-418b-b8ea-6d34fb948c06" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6f3d1eac-fac6-4c74-9e46-78c3b41a683f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_d696dc1e-b171-418b-b8ea-6d34fb948c06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParentMember_3154bb60-c777-49f9-8657-5f974fa2b8ba" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6f3d1eac-fac6-4c74-9e46-78c3b41a683f" xlink:to="loc_us-gaap_ParentMember_3154bb60-c777-49f9-8657-5f974fa2b8ba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_bef05b40-7cec-4e29-85e0-cd3bc6ea5c48" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_bef05b40-7cec-4e29-85e0-cd3bc6ea5c48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7432b3fe-fb51-4134-8332-f795150cfe81" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockholdersEquity_7432b3fe-fb51-4134-8332-f795150cfe81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_026f9fc9-22c3-46dd-8ea7-b3a1b3d25a0b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_NetIncomeLoss_026f9fc9-22c3-46dd-8ea7-b3a1b3d25a0b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_e1c27321-9ebf-4400-92be-090cc3cfcc1d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_ProfitLoss_e1c27321-9ebf-4400-92be-090cc3cfcc1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_25a32686-7b80-4c16-85cb-64fa64955203" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_25a32686-7b80-4c16-85cb-64fa64955203" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCash_6a160874-6231-45df-9cc0-84b92ec9946e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DividendsCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_DividendsCash_6a160874-6231-45df-9cc0-84b92ec9946e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_4b8df380-e275-40d0-b045-507d58ff6f04" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_4b8df380-e275-40d0-b045-507d58ff6f04" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_6c2f4be6-fb76-4429-9f32-873e6d5f2c08" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_6c2f4be6-fb76-4429-9f32-873e6d5f2c08" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_dbdf5c4e-4136-4b99-a66c-83113043ab84" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_dbdf5c4e-4136-4b99-a66c-83113043ab84" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_6a29d108-01c0-4f79-801c-17f072ca8a69" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_6a29d108-01c0-4f79-801c-17f072ca8a69" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationGross_595e58e8-415b-47c8-8c5d-104bd37f1efd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationGross_595e58e8-415b-47c8-8c5d-104bd37f1efd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_943e08d0-8065-4aa2-96ab-29e6be7ba2fa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_cb2223df-1d04-4cf3-aaef-c01e7d6328cf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesIssuedForServices_364df375-716e-4a40-a9c7-d00cc4052954" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesIssuedForServices"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesIssuedForServices_364df375-716e-4a40-a9c7-d00cc4052954" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueIssuedForServices_62462180-72b2-4c3b-a093-f9297ef8a330" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueIssuedForServices"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueIssuedForServices_62462180-72b2-4c3b-a093-f9297ef8a330" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_161f34ec-5944-425c-8a33-bbd2d32dce30" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_161f34ec-5944-425c-8a33-bbd2d32dce30" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_5f0b0d41-8ba6-490f-9eb2-5ee80b78430f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_5f0b0d41-8ba6-490f-9eb2-5ee80b78430f" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_456dbcf0-bd4b-425b-b5c1-9c998b7cd51f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_456dbcf0-bd4b-425b-b5c1-9c998b7cd51f" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_f17f9267-7b26-4618-8432-4d2d98ae142d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_srt_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_f17f9267-7b26-4618-8432-4d2d98ae142d" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_f630135a-320a-43c8-9011-70501cec36ce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_f630135a-320a-43c8-9011-70501cec36ce" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_2ca68ce5-3130-477a-84c9-4144b0fc595b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_416bf262-598d-4b5b-b584-ed3536ab3572" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_2ca68ce5-3130-477a-84c9-4144b0fc595b" xlink:type="arc" order="20"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/SubsequentEventsNotes" xlink:type="simple" xlink:href="cme-20250930.xsd#SubsequentEventsNotes"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/SubsequentEventsNotes" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_2b0c3452-2b0e-4396-8405-cb90e7da3357" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_7966b5fd-c2e4-4337-8c44-6b11b40309a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_2b0c3452-2b0e-4396-8405-cb90e7da3357" xlink:to="loc_us-gaap_SubsequentEventTable_7966b5fd-c2e4-4337-8c44-6b11b40309a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_b5632010-de86-450e-8434-005bea0d3ca6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_7966b5fd-c2e4-4337-8c44-6b11b40309a5" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_b5632010-de86-450e-8434-005bea0d3ca6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_b5632010-de86-450e-8434-005bea0d3ca6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_b5632010-de86-450e-8434-005bea0d3ca6" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_b5632010-de86-450e-8434-005bea0d3ca6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3e7845fa-7855-49f5-80d6-5900d7eada4d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_b5632010-de86-450e-8434-005bea0d3ca6" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3e7845fa-7855-49f5-80d6-5900d7eada4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventsTextBlock_45953f42-0346-4510-9c4a-d35d92f4cb59" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventsTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_2b0c3452-2b0e-4396-8405-cb90e7da3357" xlink:to="loc_us-gaap_SubsequentEventsTextBlock_45953f42-0346-4510-9c4a-d35d92f4cb59" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/FairValueMeasurementsTables" xlink:type="simple" xlink:href="cme-20250930.xsd#FairValueMeasurementsTables"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/FairValueMeasurementsTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_4647bcd5-1075-4aab-99f4-a27dd12baca1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_f4c109f2-8b44-429c-878b-33bba76fa8df" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_4647bcd5-1075-4aab-99f4-a27dd12baca1" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_f4c109f2-8b44-429c-878b-33bba76fa8df" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_85e5551a-c5d5-45b5-961a-47c9b29ecc8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_f4c109f2-8b44-429c-878b-33bba76fa8df" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_85e5551a-c5d5-45b5-961a-47c9b29ecc8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_85e5551a-c5d5-45b5-961a-47c9b29ecc8c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_85e5551a-c5d5-45b5-961a-47c9b29ecc8c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_85e5551a-c5d5-45b5-961a-47c9b29ecc8c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_3c211a0b-318a-41c8-b4f9-2a2483d93482" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_85e5551a-c5d5-45b5-961a-47c9b29ecc8c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_3c211a0b-318a-41c8-b4f9-2a2483d93482" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_de43c688-8e07-4cd1-9677-8a5bb6c67a05" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_f4c109f2-8b44-429c-878b-33bba76fa8df" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_de43c688-8e07-4cd1-9677-8a5bb6c67a05" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_de43c688-8e07-4cd1-9677-8a5bb6c67a05_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_de43c688-8e07-4cd1-9677-8a5bb6c67a05" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_de43c688-8e07-4cd1-9677-8a5bb6c67a05_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_b1732b4c-6545-448b-87a7-f6480c4b77b0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_de43c688-8e07-4cd1-9677-8a5bb6c67a05" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_b1732b4c-6545-448b-87a7-f6480c4b77b0" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/RevenueRecognitionDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#RevenueRecognitionDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/RevenueRecognitionDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_45424f15-8a58-4fae-b170-2008bcd12ad7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_a48898d1-7c7f-4a3f-af49-73ec407e64f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_45424f15-8a58-4fae-b170-2008bcd12ad7" xlink:to="loc_us-gaap_StatementTable_a48898d1-7c7f-4a3f-af49-73ec407e64f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_7bf21986-b754-4f81-9bd3-06a099f97df0" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_a48898d1-7c7f-4a3f-af49-73ec407e64f2" xlink:to="loc_srt_ProductOrServiceAxis_7bf21986-b754-4f81-9bd3-06a099f97df0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_7bf21986-b754-4f81-9bd3-06a099f97df0_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_7bf21986-b754-4f81-9bd3-06a099f97df0" xlink:to="loc_srt_ProductsAndServicesDomain_7bf21986-b754-4f81-9bd3-06a099f97df0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c5a9171a-b0a4-46f1-8a87-4ed303c3da60" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_7bf21986-b754-4f81-9bd3-06a099f97df0" xlink:to="loc_srt_ProductsAndServicesDomain_c5a9171a-b0a4-46f1-8a87-4ed303c3da60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ClearingandtransactionfeesMember_45aff47a-f2ba-40c0-86d2-26eaa3e59723" xlink:href="cme-20250930.xsd#cme_ClearingandtransactionfeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c5a9171a-b0a4-46f1-8a87-4ed303c3da60" xlink:to="loc_cme_ClearingandtransactionfeesMember_45aff47a-f2ba-40c0-86d2-26eaa3e59723" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_MarketDataMember_4655a99e-0576-4c46-ad59-71b0835f41ae" xlink:href="cme-20250930.xsd#cme_MarketDataMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c5a9171a-b0a4-46f1-8a87-4ed303c3da60" xlink:to="loc_cme_MarketDataMember_4655a99e-0576-4c46-ad59-71b0835f41ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_OtherRevenueMember_08e1a5a5-579a-4221-81c5-d6160fc1ff66" xlink:href="cme-20250930.xsd#cme_OtherRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c5a9171a-b0a4-46f1-8a87-4ed303c3da60" xlink:to="loc_cme_OtherRevenueMember_08e1a5a5-579a-4221-81c5-d6160fc1ff66" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_7e2cb200-33c0-4a64-a81b-a7b09fe2e820" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_a48898d1-7c7f-4a3f-af49-73ec407e64f2" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_7e2cb200-33c0-4a64-a81b-a7b09fe2e820" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7e2cb200-33c0-4a64-a81b-a7b09fe2e820_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_7e2cb200-33c0-4a64-a81b-a7b09fe2e820" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7e2cb200-33c0-4a64-a81b-a7b09fe2e820_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_7e2cb200-33c0-4a64-a81b-a7b09fe2e820" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_InterestRateMember_5e074501-00bc-4c08-aee9-f964efad9a6a" xlink:href="cme-20250930.xsd#cme_InterestRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_cme_InterestRateMember_5e074501-00bc-4c08-aee9-f964efad9a6a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_EquitiesMember_726af9ac-e4c3-44d9-ab86-1c957c704fa3" xlink:href="cme-20250930.xsd#cme_EquitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_cme_EquitiesMember_726af9ac-e4c3-44d9-ab86-1c957c704fa3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeMember_2c58bfe2-63d8-42b2-892d-0369fbf4d0cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_us-gaap_ForeignExchangeMember_2c58bfe2-63d8-42b2-892d-0369fbf4d0cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_AgriculturalcommodityMember_0f65ef03-1181-4555-b728-c76815bf623b" xlink:href="cme-20250930.xsd#cme_AgriculturalcommodityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_cme_AgriculturalcommodityMember_0f65ef03-1181-4555-b728-c76815bf623b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_EnergyMember_c6a1d0fc-1c0a-49b0-9397-bc03c0032b46" xlink:href="cme-20250930.xsd#cme_EnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_cme_EnergyMember_c6a1d0fc-1c0a-49b0-9397-bc03c0032b46" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_MetalMember_82ec0c95-258a-4194-907b-2d56e31d0a78" xlink:href="cme-20250930.xsd#cme_MetalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_cme_MetalMember_82ec0c95-258a-4194-907b-2d56e31d0a78" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_95c69c50-7493-40b9-bebc-677dfef2dca9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_us-gaap_InterestRateSwapMember_95c69c50-7493-40b9-bebc-677dfef2dca9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_BrokerTecFixedIncomeMember_955f0fa4-7d19-4a98-a34f-63e00f4a642c" xlink:href="cme-20250930.xsd#cme_BrokerTecFixedIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_cme_BrokerTecFixedIncomeMember_955f0fa4-7d19-4a98-a34f-63e00f4a642c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_EBSForeignExchangeMember_77942e90-ff70-43d2-a96c-cc3d41b449f0" xlink:href="cme-20250930.xsd#cme_EBSForeignExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7a272f0b-dda6-4d44-a1b4-238f44b8ae67" xlink:to="loc_cme_EBSForeignExchangeMember_77942e90-ff70-43d2-a96c-cc3d41b449f0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_658fee78-85a7-4d16-a8d3-c40ac5986066" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_a48898d1-7c7f-4a3f-af49-73ec407e64f2" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_658fee78-85a7-4d16-a8d3-c40ac5986066" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_658fee78-85a7-4d16-a8d3-c40ac5986066_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_658fee78-85a7-4d16-a8d3-c40ac5986066" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_658fee78-85a7-4d16-a8d3-c40ac5986066_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_04f6271e-d15a-4d31-8e88-0f5afc5609d9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_658fee78-85a7-4d16-a8d3-c40ac5986066" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_04f6271e-d15a-4d31-8e88-0f5afc5609d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredAtPointInTimeMember_c884a360-a6d0-42ca-8f86-d83ce18953aa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransferredAtPointInTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_04f6271e-d15a-4d31-8e88-0f5afc5609d9" xlink:to="loc_us-gaap_TransferredAtPointInTimeMember_c884a360-a6d0-42ca-8f86-d83ce18953aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredOverTimeMember_656bb6b8-02df-49e6-aa22-dff61db6e574" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransferredOverTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_04f6271e-d15a-4d31-8e88-0f5afc5609d9" xlink:to="loc_us-gaap_TransferredOverTimeMember_656bb6b8-02df-49e6-aa22-dff61db6e574" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_OnetimechargesandmiscellaneousrevenuesMember_04528cb2-2060-4f59-b499-6f0c36ae5ef7" xlink:href="cme-20250930.xsd#cme_OnetimechargesandmiscellaneousrevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_04f6271e-d15a-4d31-8e88-0f5afc5609d9" xlink:to="loc_cme_OnetimechargesandmiscellaneousrevenuesMember_04528cb2-2060-4f59-b499-6f0c36ae5ef7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c9eb99cc-9f5a-41d6-b918-c2adb41d3f59" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_45424f15-8a58-4fae-b170-2008bcd12ad7" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c9eb99cc-9f5a-41d6-b918-c2adb41d3f59" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_faec3064-c818-4185-8ba0-0aa67afcff0d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_45424f15-8a58-4fae-b170-2008bcd12ad7" xlink:to="loc_us-gaap_Revenues_faec3064-c818-4185-8ba0-0aa67afcff0d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/PerformanceBondsandGuarantyFundContributionsDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#PerformanceBondsandGuarantyFundContributionsDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/PerformanceBondsandGuarantyFundContributionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_d104c287-6034-4a13-b9ec-0870d210fbef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_d104c287-6034-4a13-b9ec-0870d210fbef" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_0b74fe57-4c28-4d5d-836a-52f3ddc65408" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_d104c287-6034-4a13-b9ec-0870d210fbef" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_0b74fe57-4c28-4d5d-836a-52f3ddc65408" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_0b74fe57-4c28-4d5d-836a-52f3ddc65408_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_0b74fe57-4c28-4d5d-836a-52f3ddc65408" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_0b74fe57-4c28-4d5d-836a-52f3ddc65408_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_0d6f422a-1caa-4bbf-b6d1-ad7692fca633" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_0b74fe57-4c28-4d5d-836a-52f3ddc65408" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_0d6f422a-1caa-4bbf-b6d1-ad7692fca633" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalReserveBankAdvancesMember_1522e42f-23d9-46e1-a539-6b650993a199" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FederalReserveBankAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_0d6f422a-1caa-4bbf-b6d1-ad7692fca633" xlink:to="loc_us-gaap_FederalReserveBankAdvancesMember_1522e42f-23d9-46e1-a539-6b650993a199" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_37fcfc8d-30fb-462d-b9f2-bec905b723db" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_d104c287-6034-4a13-b9ec-0870d210fbef" xlink:to="loc_srt_ProductOrServiceAxis_37fcfc8d-30fb-462d-b9f2-bec905b723db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_37fcfc8d-30fb-462d-b9f2-bec905b723db_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_37fcfc8d-30fb-462d-b9f2-bec905b723db" xlink:to="loc_srt_ProductsAndServicesDomain_37fcfc8d-30fb-462d-b9f2-bec905b723db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_965bb193-315d-45b0-ad36-c7681d121349" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_37fcfc8d-30fb-462d-b9f2-bec905b723db" xlink:to="loc_srt_ProductsAndServicesDomain_965bb193-315d-45b0-ad36-c7681d121349" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_InterestFromPerformanceBondsMember_652002bd-c16c-4eed-be97-2f988b7b5e66" xlink:href="cme-20250930.xsd#cme_InterestFromPerformanceBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_965bb193-315d-45b0-ad36-c7681d121349" xlink:to="loc_cme_InterestFromPerformanceBondsMember_652002bd-c16c-4eed-be97-2f988b7b5e66" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ExpenseRelatedToPerformanceBondsMember_1b3c0a47-f689-4afd-9849-461792a8f673" xlink:href="cme-20250930.xsd#cme_ExpenseRelatedToPerformanceBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_965bb193-315d-45b0-ad36-c7681d121349" xlink:to="loc_cme_ExpenseRelatedToPerformanceBondsMember_1b3c0a47-f689-4afd-9849-461792a8f673" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_AverageDailyClearingSettlement_535e28b0-4403-43b4-88e3-f38e108e90be" xlink:href="cme-20250930.xsd#cme_AverageDailyClearingSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:to="loc_cme_AverageDailyClearingSettlement_535e28b0-4403-43b4-88e3-f38e108e90be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_9ae29c59-9205-446b-9032-c5e589206875" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_9ae29c59-9205-446b-9032-c5e589206875" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_MarginDepositsAndGuarantyFundsLiabilitiesCurrent_cc12b00e-be9b-450f-a228-83bb5366b6f7" xlink:href="cme-20250930.xsd#cme_MarginDepositsAndGuarantyFundsLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:to="loc_cme_MarginDepositsAndGuarantyFundsLiabilitiesCurrent_cc12b00e-be9b-450f-a228-83bb5366b6f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_1cf34883-5548-4d59-beb9-a6787f5bf54a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_1cf34883-5548-4d59-beb9-a6787f5bf54a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeNonoperating_1ef933ed-ecd2-4b6d-8b88-d3dd7db5e926" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentIncomeNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:to="loc_us-gaap_InvestmentIncomeNonoperating_1ef933ed-ecd2-4b6d-8b88-d3dd7db5e926" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_69e0f2b7-55d5-4b86-97a8-7714699b6450" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c1fa3995-bc86-455e-9b09-0ad040359b2f" xlink:to="loc_us-gaap_Revenues_69e0f2b7-55d5-4b86-97a8-7714699b6450" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/IntangibleAssetsAndGoodwillComponentsOfIntangibleAssetsDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#IntangibleAssetsAndGoodwillComponentsOfIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/IntangibleAssetsAndGoodwillComponentsOfIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_597126cb-b015-4f1a-8939-5c79f5b3fb96" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_597126cb-b015-4f1a-8939-5c79f5b3fb96" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_dba4647f-dae0-4aa6-9552-8fb8fe1e4d44" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_597126cb-b015-4f1a-8939-5c79f5b3fb96" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_dba4647f-dae0-4aa6-9552-8fb8fe1e4d44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_dba4647f-dae0-4aa6-9552-8fb8fe1e4d44_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_dba4647f-dae0-4aa6-9552-8fb8fe1e4d44" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_dba4647f-dae0-4aa6-9552-8fb8fe1e4d44_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47e86b8f-036a-4cc8-91d7-506405e94771" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_dba4647f-dae0-4aa6-9552-8fb8fe1e4d44" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47e86b8f-036a-4cc8-91d7-506405e94771" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_c06f3597-41ff-45ba-8f2d-143e65259c49" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47e86b8f-036a-4cc8-91d7-506405e94771" xlink:to="loc_us-gaap_CustomerRelationshipsMember_c06f3597-41ff-45ba-8f2d-143e65259c49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_1652970a-c4b3-4dd5-8ebe-821f414abd8b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47e86b8f-036a-4cc8-91d7-506405e94771" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_1652970a-c4b3-4dd5-8ebe-821f414abd8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_71caf7b1-681d-4558-b684-a54c3ce452b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47e86b8f-036a-4cc8-91d7-506405e94771" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_71caf7b1-681d-4558-b684-a54c3ce452b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMember_1de7ae27-5e9d-43c3-b40e-c5e30bf4afd7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47e86b8f-036a-4cc8-91d7-506405e94771" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMember_1de7ae27-5e9d-43c3-b40e-c5e30bf4afd7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_163ebf0a-7e9e-477e-91ce-38be4d1d5c6c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_597126cb-b015-4f1a-8939-5c79f5b3fb96" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_163ebf0a-7e9e-477e-91ce-38be4d1d5c6c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_163ebf0a-7e9e-477e-91ce-38be4d1d5c6c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_163ebf0a-7e9e-477e-91ce-38be4d1d5c6c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_163ebf0a-7e9e-477e-91ce-38be4d1d5c6c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_09376df0-ce79-4d0b-97c8-7354e1fbf4c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_163ebf0a-7e9e-477e-91ce-38be4d1d5c6c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_09376df0-ce79-4d0b-97c8-7354e1fbf4c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_f06c84a6-9267-4092-a2e9-14528173fc21" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_09376df0-ce79-4d0b-97c8-7354e1fbf4c6" xlink:to="loc_us-gaap_TradeNamesMember_f06c84a6-9267-4092-a2e9-14528173fc21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_0d127497-0470-4040-9704-aab1a379709a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_0d127497-0470-4040-9704-aab1a379709a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_d4803469-283c-4d7c-b14d-3d4454e675fc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_d4803469-283c-4d7c-b14d-3d4454e675fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_497de0ac-42bc-4898-bdbb-ad7d93cc635b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_497de0ac-42bc-4898-bdbb-ad7d93cc635b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_b625ab21-fd8e-465d-af81-a6b7f20782b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_b625ab21-fd8e-465d-af81-a6b7f20782b1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIndefiniteLivedIntangibleAssets_690e281d-f21e-4294-8143-5d46d504e0e0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherIndefiniteLivedIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:to="loc_us-gaap_OtherIndefiniteLivedIntangibleAssets_690e281d-f21e-4294-8143-5d46d504e0e0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_Intangibleassetstradingproducts_2304fa18-64b1-44df-a443-da75cd9c3afe" xlink:href="cme-20250930.xsd#cme_Intangibleassetstradingproducts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e42ad307-a665-40d0-976a-603ccbe4b789" xlink:to="loc_cme_Intangibleassetstradingproducts_2304fa18-64b1-44df-a443-da75cd9c3afe" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/IntangibleAssetsAndGoodwillComponentsofGoodwillDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#IntangibleAssetsAndGoodwillComponentsofGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/IntangibleAssetsAndGoodwillComponentsofGoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_eeb4176c-ad00-4006-bb21-26c4cfdbec53" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_a2ed0593-5ed7-412a-9bdf-6b31b74ba5d8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_eeb4176c-ad00-4006-bb21-26c4cfdbec53" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_a2ed0593-5ed7-412a-9bdf-6b31b74ba5d8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_ee218abd-d547-4cc7-b22a-1b435f42a68f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_a2ed0593-5ed7-412a-9bdf-6b31b74ba5d8" xlink:to="loc_srt_ConsolidationItemsAxis_ee218abd-d547-4cc7-b22a-1b435f42a68f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_ee218abd-d547-4cc7-b22a-1b435f42a68f_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_ee218abd-d547-4cc7-b22a-1b435f42a68f" xlink:to="loc_srt_ConsolidationItemsDomain_ee218abd-d547-4cc7-b22a-1b435f42a68f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_9b0d40a5-5056-4ce8-9b46-e82eef1bfbdd" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_ee218abd-d547-4cc7-b22a-1b435f42a68f" xlink:to="loc_srt_ConsolidationItemsDomain_9b0d40a5-5056-4ce8-9b46-e82eef1bfbdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_85acc93c-b5e2-4677-a111-d33c00e4110f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_eeb4176c-ad00-4006-bb21-26c4cfdbec53" xlink:to="loc_us-gaap_Goodwill_85acc93c-b5e2-4677-a111-d33c00e4110f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_604cdd1d-8387-422f-8bb4-f65ecdaf7d4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_eeb4176c-ad00-4006-bb21-26c4cfdbec53" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_604cdd1d-8387-422f-8bb4-f65ecdaf7d4c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/DebtScheduleOfShortTermAndLongTermDebtDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#DebtScheduleOfShortTermAndLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/DebtScheduleOfShortTermAndLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_4fbd0468-d650-4786-8e66-b5ffab251737" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:to="loc_us-gaap_StatementTable_4fbd0468-d650-4786-8e66-b5ffab251737" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_21d8a9e9-ad5d-40f0-ab1d-3bef9420b2e8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_4fbd0468-d650-4786-8e66-b5ffab251737" xlink:to="loc_us-gaap_DebtInstrumentAxis_21d8a9e9-ad5d-40f0-ab1d-3bef9420b2e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_21d8a9e9-ad5d-40f0-ab1d-3bef9420b2e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_21d8a9e9-ad5d-40f0-ab1d-3bef9420b2e8" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_21d8a9e9-ad5d-40f0-ab1d-3bef9420b2e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_21d8a9e9-ad5d-40f0-ab1d-3bef9420b2e8" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member_75b39da2-fc7c-4122-9330-4cdca75e0fad" xlink:href="cme-20250930.xsd#cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:to="loc_cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member_75b39da2-fc7c-4122-9330-4cdca75e0fad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain_33824b6e-ee87-4e7e-9093-ada5938139c7" xlink:href="cme-20250930.xsd#cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:to="loc_cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain_33824b6e-ee87-4e7e-9093-ada5938139c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0millionFixedRateNotesDueSeptember2043InterestEqualTo5.3Member_5b0c5d23-4ec6-4f65-a148-933f3bb78d23" xlink:href="cme-20250930.xsd#cme_A750.0millionFixedRateNotesDueSeptember2043InterestEqualTo5.3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:to="loc_cme_A750.0millionFixedRateNotesDueSeptember2043InterestEqualTo5.3Member_5b0c5d23-4ec6-4f65-a148-933f3bb78d23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A700.0MillionFixedRateNotesDueJune2048InterestEqualTo4.15MemberDomainDomain_8a25014d-be04-43e6-9aff-0e118df94b53" xlink:href="cme-20250930.xsd#cme_A700.0MillionFixedRateNotesDueJune2048InterestEqualTo4.15MemberDomainDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:to="loc_cme_A700.0MillionFixedRateNotesDueJune2048InterestEqualTo4.15MemberDomainDomain_8a25014d-be04-43e6-9aff-0e118df94b53" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A7500MillionFixedRateNotesDueMarch2032InterestEqualTo265Member_b739c29a-6d2e-4848-b9dc-24f473df0dec" xlink:href="cme-20250930.xsd#cme_A7500MillionFixedRateNotesDueMarch2032InterestEqualTo265Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:to="loc_cme_A7500MillionFixedRateNotesDueMarch2032InterestEqualTo265Member_b739c29a-6d2e-4848-b9dc-24f473df0dec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Abstract_44a8ec7f-98c0-40b8-b70b-9cb3c2fe7b08" xlink:href="cme-20250930.xsd#cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Abstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:to="loc_cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Abstract_44a8ec7f-98c0-40b8-b70b-9cb3c2fe7b08" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A500.0MillionFixedRateNotesDueJune2028InterestEqualTo3.75Domain_6d72df51-853c-4282-b708-7d5628805e41" xlink:href="cme-20250930.xsd#cme_A500.0MillionFixedRateNotesDueJune2028InterestEqualTo3.75Domain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_686fc4d2-cb6b-4517-86f9-145813e2b4ea" xlink:to="loc_cme_A500.0MillionFixedRateNotesDueJune2028InterestEqualTo3.75Domain_6d72df51-853c-4282-b708-7d5628805e41" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredLongTermDebt_877df18d-4da6-41fb-932d-ee55645ce4f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnsecuredLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:to="loc_us-gaap_UnsecuredLongTermDebt_877df18d-4da6-41fb-932d-ee55645ce4f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ForwardStartingInterestRateSwapAgreementFixedRate_c96fd262-627d-4af8-913b-071bbb102b27" xlink:href="cme-20250930.xsd#cme_ForwardStartingInterestRateSwapAgreementFixedRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:to="loc_cme_ForwardStartingInterestRateSwapAgreementFixedRate_c96fd262-627d-4af8-913b-071bbb102b27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_81811241-c747-4dd7-be70-0ef01449d734" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_81811241-c747-4dd7-be70-0ef01449d734" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_27d5e19c-97f5-40a9-84b1-442405cc5c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_27d5e19c-97f5-40a9-84b1-442405cc5c6f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_22d39245-d0ac-4bff-96f1-c5d037ac6818" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_22d39245-d0ac-4bff-96f1-c5d037ac6818" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_e83817f4-d07c-44a2-afd4-8421b55440fd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_356abfd1-2793-42cd-9234-2ac557813377" xlink:to="loc_us-gaap_ShortTermBorrowings_e83817f4-d07c-44a2-afd4-8421b55440fd" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/DebtNarrativedetailsDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#DebtNarrativedetailsDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/DebtNarrativedetailsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_a08a5153-914e-4076-83bf-8605967cfdbb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_44e9b91e-0fdd-4723-a3bd-f62427a2ba61" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a08a5153-914e-4076-83bf-8605967cfdbb" xlink:to="loc_us-gaap_DebtInstrumentTable_44e9b91e-0fdd-4723-a3bd-f62427a2ba61" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_0cb4ed2a-c78b-41a6-94ae-3bb23577f427" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_44e9b91e-0fdd-4723-a3bd-f62427a2ba61" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_0cb4ed2a-c78b-41a6-94ae-3bb23577f427" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0cb4ed2a-c78b-41a6-94ae-3bb23577f427_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0cb4ed2a-c78b-41a6-94ae-3bb23577f427" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0cb4ed2a-c78b-41a6-94ae-3bb23577f427_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0567ef09-e5fb-4570-994e-cae0c0f19102" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0cb4ed2a-c78b-41a6-94ae-3bb23577f427" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0567ef09-e5fb-4570-994e-cae0c0f19102" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_5089d7fb-337d-4b6b-aff3-365bd03678ee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_44e9b91e-0fdd-4723-a3bd-f62427a2ba61" xlink:to="loc_us-gaap_DebtInstrumentAxis_5089d7fb-337d-4b6b-aff3-365bd03678ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_5089d7fb-337d-4b6b-aff3-365bd03678ee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_5089d7fb-337d-4b6b-aff3-365bd03678ee" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_5089d7fb-337d-4b6b-aff3-365bd03678ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7bfd8969-e7f8-4c63-8b40-f4c7d5d5af6f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_5089d7fb-337d-4b6b-aff3-365bd03678ee" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7bfd8969-e7f8-4c63-8b40-f4c7d5d5af6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Abstract_64064c02-8bab-48dc-8dac-f55dae2dfc4b" xlink:href="cme-20250930.xsd#cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Abstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7bfd8969-e7f8-4c63-8b40-f4c7d5d5af6f" xlink:to="loc_cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Abstract_64064c02-8bab-48dc-8dac-f55dae2dfc4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member_df09ade7-8a2e-4ef1-9609-c19068f24455" xlink:href="cme-20250930.xsd#cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7bfd8969-e7f8-4c63-8b40-f4c7d5d5af6f" xlink:to="loc_cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member_df09ade7-8a2e-4ef1-9609-c19068f24455" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain_482a19f4-02b7-427f-9fad-994ce561c6de" xlink:href="cme-20250930.xsd#cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7bfd8969-e7f8-4c63-8b40-f4c7d5d5af6f" xlink:to="loc_cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain_482a19f4-02b7-427f-9fad-994ce561c6de" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_5eb4ced6-30de-421d-be77-ab4f4bcdabe3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_44e9b91e-0fdd-4723-a3bd-f62427a2ba61" xlink:to="loc_us-gaap_VariableRateAxis_5eb4ced6-30de-421d-be77-ab4f4bcdabe3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_5eb4ced6-30de-421d-be77-ab4f4bcdabe3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_5eb4ced6-30de-421d-be77-ab4f4bcdabe3" xlink:to="loc_us-gaap_VariableRateDomain_5eb4ced6-30de-421d-be77-ab4f4bcdabe3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_dd4a58b7-41ac-43aa-a8bb-0907b92a86f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_5eb4ced6-30de-421d-be77-ab4f4bcdabe3" xlink:to="loc_us-gaap_VariableRateDomain_dd4a58b7-41ac-43aa-a8bb-0907b92a86f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_6375f6ed-354d-4644-9268-f414d53ddc90" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_44e9b91e-0fdd-4723-a3bd-f62427a2ba61" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_6375f6ed-354d-4644-9268-f414d53ddc90" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_6375f6ed-354d-4644-9268-f414d53ddc90_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_6375f6ed-354d-4644-9268-f414d53ddc90" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_6375f6ed-354d-4644-9268-f414d53ddc90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_97637cab-e372-4799-be84-af509ef31b29" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_6375f6ed-354d-4644-9268-f414d53ddc90" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_97637cab-e372-4799-be84-af509ef31b29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_6cf8dbbf-666c-4b8b-b40f-9905dba71fe1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_44e9b91e-0fdd-4723-a3bd-f62427a2ba61" xlink:to="loc_srt_RangeAxis_6cf8dbbf-666c-4b8b-b40f-9905dba71fe1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_6cf8dbbf-666c-4b8b-b40f-9905dba71fe1_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_6cf8dbbf-666c-4b8b-b40f-9905dba71fe1" xlink:to="loc_srt_RangeMember_6cf8dbbf-666c-4b8b-b40f-9905dba71fe1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_e7156c98-26ec-45e5-b3ee-4380f4db4cc6" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_6cf8dbbf-666c-4b8b-b40f-9905dba71fe1" xlink:to="loc_srt_RangeMember_e7156c98-26ec-45e5-b3ee-4380f4db4cc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_ForwardStartingInterestRateSwapAgreementFixedRate_9ffe4cfb-f999-4159-a78d-82136557bf02" xlink:href="cme-20250930.xsd#cme_ForwardStartingInterestRateSwapAgreementFixedRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a08a5153-914e-4076-83bf-8605967cfdbb" xlink:to="loc_cme_ForwardStartingInterestRateSwapAgreementFixedRate_9ffe4cfb-f999-4159-a78d-82136557bf02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredLongTermDebt_c7c71870-f514-46f1-907d-98c80314c90b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnsecuredLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a08a5153-914e-4076-83bf-8605967cfdbb" xlink:to="loc_us-gaap_UnsecuredLongTermDebt_c7c71870-f514-46f1-907d-98c80314c90b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_ac07ed8a-f8bc-4aca-9852-5016b08f752c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a08a5153-914e-4076-83bf-8605967cfdbb" xlink:to="loc_us-gaap_ShortTermBorrowings_ac07ed8a-f8bc-4aca-9852-5016b08f752c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_58eca53d-4ba7-46de-8c4d-ad3cbaf53f65" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a08a5153-914e-4076-83bf-8605967cfdbb" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_58eca53d-4ba7-46de-8c4d-ad3cbaf53f65" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_a6101760-25b6-45c7-8ccf-e04173d86d3c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a08a5153-914e-4076-83bf-8605967cfdbb" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_a6101760-25b6-45c7-8ccf-e04173d86d3c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/LeasesOperatingLeasesFutureMinimumPaymentsDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#LeasesOperatingLeasesFutureMinimumPaymentsDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/LeasesOperatingLeasesFutureMinimumPaymentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_cme_OperatingLeasesFutureMinimumPaymentsDueLineItems_179370db-3494-496c-8c7d-9bff96bb339a" xlink:href="cme-20250930.xsd#cme_OperatingLeasesFutureMinimumPaymentsDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_OperatingLeasesFutureMinimumPaymentsDueTable_873168e9-fbe8-445b-82f6-6f4b47664472" xlink:href="cme-20250930.xsd#cme_OperatingLeasesFutureMinimumPaymentsDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_cme_OperatingLeasesFutureMinimumPaymentsDueLineItems_179370db-3494-496c-8c7d-9bff96bb339a" xlink:to="loc_cme_OperatingLeasesFutureMinimumPaymentsDueTable_873168e9-fbe8-445b-82f6-6f4b47664472" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_b0780974-fe49-4808-bc09-ba2cf4ca9e05" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_cme_OperatingLeasesFutureMinimumPaymentsDueTable_873168e9-fbe8-445b-82f6-6f4b47664472" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_b0780974-fe49-4808-bc09-ba2cf4ca9e05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_b0780974-fe49-4808-bc09-ba2cf4ca9e05_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_b0780974-fe49-4808-bc09-ba2cf4ca9e05" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_b0780974-fe49-4808-bc09-ba2cf4ca9e05_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_574aaf1c-2594-4645-9b54-4ae27daba97f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_b0780974-fe49-4808-bc09-ba2cf4ca9e05" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_574aaf1c-2594-4645-9b54-4ae27daba97f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/LeasesCapitalLeasesFutureMinimumPaymentsDueDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#LeasesCapitalLeasesFutureMinimumPaymentsDueDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/LeasesCapitalLeasesFutureMinimumPaymentsDueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:href="cme-20250930.xsd#cme_CapitalLeasesFutureMinimumPaymentsDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_CapitalLeasesFutureMinimumPaymentsDueTable_765a7624-ee48-43fc-9297-23646e0e80c6" xlink:href="cme-20250930.xsd#cme_CapitalLeasesFutureMinimumPaymentsDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_cme_CapitalLeasesFutureMinimumPaymentsDueTable_765a7624-ee48-43fc-9297-23646e0e80c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_73da7db2-a807-4d02-96b1-5e94e0cd1f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueTable_765a7624-ee48-43fc-9297-23646e0e80c6" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_73da7db2-a807-4d02-96b1-5e94e0cd1f1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_73da7db2-a807-4d02-96b1-5e94e0cd1f1c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_73da7db2-a807-4d02-96b1-5e94e0cd1f1c" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_73da7db2-a807-4d02-96b1-5e94e0cd1f1c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_6f1f2de2-a764-4b0c-ac12-c1af2e234d7d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis_73da7db2-a807-4d02-96b1-5e94e0cd1f1c" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseDomain_6f1f2de2-a764-4b0c-ac12-c1af2e234d7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear_48d8b2ba-bb05-4c52-9b64-e6729971521e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear_48d8b2ba-bb05-4c52-9b64-e6729971521e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_85684b68-ab7f-4ffe-b22e-5bce280f91e5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_85684b68-ab7f-4ffe-b22e-5bce280f91e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_ac84e705-25aa-4011-95e2-769e9f9cd11a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_ac84e705-25aa-4011-95e2-769e9f9cd11a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_d42f1398-06e7-4e4f-9a6e-68656743c756" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_d42f1398-06e7-4e4f-9a6e-68656743c756" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_18bc7f5e-3ac3-439d-9033-d4b80945408c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_18bc7f5e-3ac3-439d-9033-d4b80945408c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_3184981c-7615-438e-b7e8-1b146572828a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_3184981c-7615-438e-b7e8-1b146572828a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_ec5ca2d8-2e40-47ee-9b25-f8ab751237b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_ec5ca2d8-2e40-47ee-9b25-f8ab751237b1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_f0475e92-d5af-4345-90b5-0c397cffb34f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_f0475e92-d5af-4345-90b5-0c397cffb34f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_Financeleasefutureminimumpaymentsinterestimputed_21c4103a-5f89-4276-9e11-4a8da6c6fc98" xlink:href="cme-20250930.xsd#cme_Financeleasefutureminimumpaymentsinterestimputed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_cme_Financeleasefutureminimumpaymentsinterestimputed_21c4103a-5f89-4276-9e11-4a8da6c6fc98" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_Financeleasesfutureminimumpaymentspresentvalueofnetminimumpayments_37f52dd3-5699-43bf-997c-1deb9ee299b4" xlink:href="cme-20250930.xsd#cme_Financeleasesfutureminimumpaymentspresentvalueofnetminimumpayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cme_CapitalLeasesFutureMinimumPaymentsDueLineItems_512f6aa9-4714-494e-a88c-a8dc4c43adf4" xlink:to="loc_cme_Financeleasesfutureminimumpaymentspresentvalueofnetminimumpayments_37f52dd3-5699-43bf-997c-1deb9ee299b4" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/GuaranteesDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#GuaranteesDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/GuaranteesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_56d9d9ff-e25f-406e-9c3f-f52dd5982d6f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_56d9d9ff-e25f-406e-9c3f-f52dd5982d6f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_adbe35f0-474f-4351-8fa1-0d5327bb1858" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_56d9d9ff-e25f-406e-9c3f-f52dd5982d6f" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_adbe35f0-474f-4351-8fa1-0d5327bb1858" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_adbe35f0-474f-4351-8fa1-0d5327bb1858_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_adbe35f0-474f-4351-8fa1-0d5327bb1858" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_adbe35f0-474f-4351-8fa1-0d5327bb1858_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_458d097f-9f89-4054-a7f6-1338b7b1b997" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_adbe35f0-474f-4351-8fa1-0d5327bb1858" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_458d097f-9f89-4054-a7f6-1338b7b1b997" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_FamilyFarmerAndRanchersProtectionFundMember_b178ebc5-b403-4371-9ff0-d02d40a6adc4" xlink:href="cme-20250930.xsd#cme_FamilyFarmerAndRanchersProtectionFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_458d097f-9f89-4054-a7f6-1338b7b1b997" xlink:to="loc_cme_FamilyFarmerAndRanchersProtectionFundMember_b178ebc5-b403-4371-9ff0-d02d40a6adc4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_AgreementAutomaticRenewalPeriod_9d264586-7da8-4edc-b29f-4a7f9a1b7b0a" xlink:href="cme-20250930.xsd#cme_AgreementAutomaticRenewalPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_cme_AgreementAutomaticRenewalPeriod_9d264586-7da8-4edc-b29f-4a7f9a1b7b0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_GuaranteeCollateral_80eae5c3-c8f5-404a-9737-126b38048ebb" xlink:href="cme-20250930.xsd#cme_GuaranteeCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_cme_GuaranteeCollateral_80eae5c3-c8f5-404a-9737-126b38048ebb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_Paymentperparticipant_069fcb7e-bbc3-472b-b947-35a284cfeef2" xlink:href="cme-20250930.xsd#cme_Paymentperparticipant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_cme_Paymentperparticipant_069fcb7e-bbc3-472b-b947-35a284cfeef2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_Paymentpercooperative_2e2a5c22-d314-413d-83a4-e9f18e12c13e" xlink:href="cme-20250930.xsd#cme_Paymentpercooperative"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_cme_Paymentpercooperative_2e2a5c22-d314-413d-83a4-e9f18e12c13e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_Futurelosses_ba21b78a-f672-4c79-82d9-9f107a9612b2" xlink:href="cme-20250930.xsd#cme_Futurelosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_cme_Futurelosses_ba21b78a-f672-4c79-82d9-9f107a9612b2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_PaymentsunderGuarantee_4dfceea8-08c8-4d4a-a9a4-c626c833105f" xlink:href="cme-20250930.xsd#cme_PaymentsunderGuarantee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_cme_PaymentsunderGuarantee_4dfceea8-08c8-4d4a-a9a4-c626c833105f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsMaximumExposure_01600930-0a44-4d8e-ac9d-8bb358d2174c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GuaranteeObligationsMaximumExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_us-gaap_GuaranteeObligationsMaximumExposure_01600930-0a44-4d8e-ac9d-8bb358d2174c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_f94862cf-9d0b-41a6-8a92-a2311c54a887" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_c88c9a8d-75dc-4ce4-b98d-1251c86c3e3e" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_f94862cf-9d0b-41a6-8a92-a2311c54a887" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/AccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#AccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/AccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_0f085e99-bfda-4e09-992e-6682b0ae5127" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6d95dc9b-a7c2-45fe-b460-229abf6cedce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_0f085e99-bfda-4e09-992e-6682b0ae5127" xlink:to="loc_us-gaap_StatementTable_6d95dc9b-a7c2-45fe-b460-229abf6cedce" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_157e9e16-94a3-4dbb-8ad1-d4a7cd445896" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6d95dc9b-a7c2-45fe-b460-229abf6cedce" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_157e9e16-94a3-4dbb-8ad1-d4a7cd445896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_157e9e16-94a3-4dbb-8ad1-d4a7cd445896_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_157e9e16-94a3-4dbb-8ad1-d4a7cd445896" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_157e9e16-94a3-4dbb-8ad1-d4a7cd445896_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_9d8a36ab-1891-4776-b603-2dd7dc032fe7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_157e9e16-94a3-4dbb-8ad1-d4a7cd445896" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_9d8a36ab-1891-4776-b603-2dd7dc032fe7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_d54ff004-8ab7-4bbe-a237-55b2f2592552" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_9d8a36ab-1891-4776-b603-2dd7dc032fe7" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_d54ff004-8ab7-4bbe-a237-55b2f2592552" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_2bae9356-01ec-4097-acb4-2cd50e8c6a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_9d8a36ab-1891-4776-b603-2dd7dc032fe7" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_2bae9356-01ec-4097-acb4-2cd50e8c6a1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_a5f11ad5-cd6b-4ba3-b357-006cf651af18" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_9d8a36ab-1891-4776-b603-2dd7dc032fe7" xlink:to="loc_us-gaap_CashFlowHedgingMember_a5f11ad5-cd6b-4ba3-b357-006cf651af18" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyGainLossMember_43006fce-8aa9-479e-bca0-d583ef446152" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignCurrencyGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_9d8a36ab-1891-4776-b603-2dd7dc032fe7" xlink:to="loc_us-gaap_ForeignCurrencyGainLossMember_43006fce-8aa9-479e-bca0-d583ef446152" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b48a3dce-2988-4d1b-9533-c4db193d39df" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_9d8a36ab-1891-4776-b603-2dd7dc032fe7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b48a3dce-2988-4d1b-9533-c4db193d39df" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_f62d490b-aa07-4f73-ae8b-225f103c18a1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f085e99-bfda-4e09-992e-6682b0ae5127" xlink:to="loc_us-gaap_StockholdersEquity_f62d490b-aa07-4f73-ae8b-225f103c18a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_18070f57-7100-4cc3-b3bb-db8e2e2eabce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f085e99-bfda-4e09-992e-6682b0ae5127" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_18070f57-7100-4cc3-b3bb-db8e2e2eabce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_6bc1c3b0-2320-4db2-a0a5-b6128d5da31c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f085e99-bfda-4e09-992e-6682b0ae5127" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_6bc1c3b0-2320-4db2-a0a5-b6128d5da31c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_afce1f2d-4ef7-45b2-beff-dd45e08d4d9e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f085e99-bfda-4e09-992e-6682b0ae5127" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_afce1f2d-4ef7-45b2-beff-dd45e08d4d9e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_21c45c30-6f8c-4e28-bfd3-3b717c722b47" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0f085e99-bfda-4e09-992e-6682b0ae5127" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_21c45c30-6f8c-4e28-bfd3-3b717c722b47" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_6bf740f5-6683-445c-9358-5323efac406e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#FairValueMeasurementsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_93f47f59-dec3-47f1-a74d-7471fe819fb2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8e201b40-1e7f-4d9d-ae58-9fb767631de3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_93f47f59-dec3-47f1-a74d-7471fe819fb2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8e201b40-1e7f-4d9d-ae58-9fb767631de3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_9295d135-4798-4f21-a87e-fdc8e89ba265" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8e201b40-1e7f-4d9d-ae58-9fb767631de3" xlink:to="loc_us-gaap_InvestmentTypeAxis_9295d135-4798-4f21-a87e-fdc8e89ba265" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_9295d135-4798-4f21-a87e-fdc8e89ba265_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_9295d135-4798-4f21-a87e-fdc8e89ba265" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_9295d135-4798-4f21-a87e-fdc8e89ba265_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_1645b719-8484-4838-9a3c-3f826efd8165" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_9295d135-4798-4f21-a87e-fdc8e89ba265" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_1645b719-8484-4838-9a3c-3f826efd8165" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_40a1f8d3-796d-46bb-bdd1-e9d031816947" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8e201b40-1e7f-4d9d-ae58-9fb767631de3" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_40a1f8d3-796d-46bb-bdd1-e9d031816947" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_40a1f8d3-796d-46bb-bdd1-e9d031816947_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_40a1f8d3-796d-46bb-bdd1-e9d031816947" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_40a1f8d3-796d-46bb-bdd1-e9d031816947_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_36150575-340c-40a8-bc12-c48a04119c49" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_40a1f8d3-796d-46bb-bdd1-e9d031816947" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_36150575-340c-40a8-bc12-c48a04119c49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_cd020a18-4464-41bd-89c5-418a6a1d7308" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_36150575-340c-40a8-bc12-c48a04119c49" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_cd020a18-4464-41bd-89c5-418a6a1d7308" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_dd83a8b7-ebfe-4c61-845b-97819cd710c4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8e201b40-1e7f-4d9d-ae58-9fb767631de3" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_dd83a8b7-ebfe-4c61-845b-97819cd710c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_dd83a8b7-ebfe-4c61-845b-97819cd710c4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_dd83a8b7-ebfe-4c61-845b-97819cd710c4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_dd83a8b7-ebfe-4c61-845b-97819cd710c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_469ecb7c-68a5-4811-902b-aa2b28d09a0e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_dd83a8b7-ebfe-4c61-845b-97819cd710c4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_469ecb7c-68a5-4811-902b-aa2b28d09a0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_67e6c136-f667-4d91-bae0-8b13e33e4551" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8e201b40-1e7f-4d9d-ae58-9fb767631de3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_67e6c136-f667-4d91-bae0-8b13e33e4551" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_67e6c136-f667-4d91-bae0-8b13e33e4551_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_67e6c136-f667-4d91-bae0-8b13e33e4551" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_67e6c136-f667-4d91-bae0-8b13e33e4551_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_5e9c0298-4e1e-4b4e-a2b5-2ba16f6c99d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_67e6c136-f667-4d91-bae0-8b13e33e4551" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_5e9c0298-4e1e-4b4e-a2b5-2ba16f6c99d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_3150fbf2-6476-40c7-b8bc-0efe8ab562be" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_93f47f59-dec3-47f1-a74d-7471fe819fb2" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_3150fbf2-6476-40c7-b8bc-0efe8ab562be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_8940d709-7dbf-48c9-acc3-7b12c8cbdc34" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_93f47f59-dec3-47f1-a74d-7471fe819fb2" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_8940d709-7dbf-48c9-acc3-7b12c8cbdc34" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/FairValueMeasurementsFinancialInstrumentsMeasuredAtFairValueOnARecurringBasisDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#FairValueMeasurementsFinancialInstrumentsMeasuredAtFairValueOnARecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/FairValueMeasurementsFinancialInstrumentsMeasuredAtFairValueOnARecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_071c8dca-77af-4b04-bc6b-1725c4b4d3ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_5acd485b-5e4c-4547-82f6-7378d6cd1412" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_071c8dca-77af-4b04-bc6b-1725c4b4d3ae" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_5acd485b-5e4c-4547-82f6-7378d6cd1412" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a22abdfe-91af-46ba-b27e-af6d643cf413" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_5acd485b-5e4c-4547-82f6-7378d6cd1412" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a22abdfe-91af-46ba-b27e-af6d643cf413" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_a22abdfe-91af-46ba-b27e-af6d643cf413_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a22abdfe-91af-46ba-b27e-af6d643cf413" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_a22abdfe-91af-46ba-b27e-af6d643cf413_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_452f4137-da6c-456f-ac1e-f9db78d7f794" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a22abdfe-91af-46ba-b27e-af6d643cf413" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_452f4137-da6c-456f-ac1e-f9db78d7f794" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_44d846df-2a44-44cd-87ca-8b0a9ad695c4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_452f4137-da6c-456f-ac1e-f9db78d7f794" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_44d846df-2a44-44cd-87ca-8b0a9ad695c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ae2f6f3e-64fd-4abe-bc5e-85405b80a5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_5acd485b-5e4c-4547-82f6-7378d6cd1412" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ae2f6f3e-64fd-4abe-bc5e-85405b80a5f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_ae2f6f3e-64fd-4abe-bc5e-85405b80a5f7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ae2f6f3e-64fd-4abe-bc5e-85405b80a5f7" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_ae2f6f3e-64fd-4abe-bc5e-85405b80a5f7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fc4a451e-6d1d-44f1-bacf-6a47b2df0768" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ae2f6f3e-64fd-4abe-bc5e-85405b80a5f7" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fc4a451e-6d1d-44f1-bacf-6a47b2df0768" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_036d3b62-a01e-4dde-a537-102d438fe420" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fc4a451e-6d1d-44f1-bacf-6a47b2df0768" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_036d3b62-a01e-4dde-a537-102d438fe420" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_3d27b58d-25e3-4534-be56-32a76bfdd013" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fc4a451e-6d1d-44f1-bacf-6a47b2df0768" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_3d27b58d-25e3-4534-be56-32a76bfdd013" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_f24951b8-4839-4a20-948f-a6b00dff4954" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fc4a451e-6d1d-44f1-bacf-6a47b2df0768" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_f24951b8-4839-4a20-948f-a6b00dff4954" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_eb931e66-5424-4df9-802e-2a4b8ce8ae15" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_5acd485b-5e4c-4547-82f6-7378d6cd1412" xlink:to="loc_us-gaap_FinancialInstrumentAxis_eb931e66-5424-4df9-802e-2a4b8ce8ae15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eb931e66-5424-4df9-802e-2a4b8ce8ae15_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_eb931e66-5424-4df9-802e-2a4b8ce8ae15" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eb931e66-5424-4df9-802e-2a4b8ce8ae15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6279629e-61e3-41fa-87ed-bbb533e27397" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_eb931e66-5424-4df9-802e-2a4b8ce8ae15" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6279629e-61e3-41fa-87ed-bbb533e27397" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_a4a058a3-fe34-427b-8f4e-1be5ca10dbc2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6279629e-61e3-41fa-87ed-bbb533e27397" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_a4a058a3-fe34-427b-8f4e-1be5ca10dbc2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MutualFundMember_8d83cce7-1177-4fad-b242-989913819e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MutualFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6279629e-61e3-41fa-87ed-bbb533e27397" xlink:to="loc_us-gaap_MutualFundMember_8d83cce7-1177-4fad-b242-989913819e5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_d7b90809-8786-484e-9ee0-2a6fe36837af" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6279629e-61e3-41fa-87ed-bbb533e27397" xlink:to="loc_us-gaap_EquitySecuritiesMember_d7b90809-8786-484e-9ee0-2a6fe36837af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecurities_fede90df-aebf-48f4-b437-3b671bf0052d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TradingSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_071c8dca-77af-4b04-bc6b-1725c4b4d3ae" xlink:to="loc_us-gaap_TradingSecurities_fede90df-aebf-48f4-b437-3b671bf0052d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecurities_9586dd82-d3a5-415a-8ddf-71573178f3c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_071c8dca-77af-4b04-bc6b-1725c4b4d3ae" xlink:to="loc_us-gaap_MarketableSecurities_9586dd82-d3a5-415a-8ddf-71573178f3c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_89a6ee18-a26f-407f-9827-16c3d5b2e1f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_071c8dca-77af-4b04-bc6b-1725c4b4d3ae" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_89a6ee18-a26f-407f-9827-16c3d5b2e1f9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/FairValueMeasurementsEstimatedFairValuesofLongTermDebtDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#FairValueMeasurementsEstimatedFairValuesofLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/FairValueMeasurementsEstimatedFairValuesofLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_b7abfd5d-9566-4193-87e5-e0edb8f99d3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_bef8facd-1c40-41c5-ba01-fd269330b3d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_b7abfd5d-9566-4193-87e5-e0edb8f99d3a" xlink:to="loc_us-gaap_StatementTable_bef8facd-1c40-41c5-ba01-fd269330b3d1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9561d71-3ecd-43e8-9255-cd8e302233e8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bef8facd-1c40-41c5-ba01-fd269330b3d1" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9561d71-3ecd-43e8-9255-cd8e302233e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c9561d71-3ecd-43e8-9255-cd8e302233e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9561d71-3ecd-43e8-9255-cd8e302233e8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c9561d71-3ecd-43e8-9255-cd8e302233e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_6d7b33af-1e9e-4de1-8ede-a9aee93a8fff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9561d71-3ecd-43e8-9255-cd8e302233e8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_6d7b33af-1e9e-4de1-8ede-a9aee93a8fff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_9be3d431-9bb4-49b5-b8e8-a0a52049eb44" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_6d7b33af-1e9e-4de1-8ede-a9aee93a8fff" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_9be3d431-9bb4-49b5-b8e8-a0a52049eb44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_37f6206e-cf1c-4a29-a42e-756fdbdd1117" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_6d7b33af-1e9e-4de1-8ede-a9aee93a8fff" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_37f6206e-cf1c-4a29-a42e-756fdbdd1117" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_4dbfc860-8691-4de7-99d5-64b443556699" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bef8facd-1c40-41c5-ba01-fd269330b3d1" xlink:to="loc_us-gaap_DebtInstrumentAxis_4dbfc860-8691-4de7-99d5-64b443556699" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4dbfc860-8691-4de7-99d5-64b443556699_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_4dbfc860-8691-4de7-99d5-64b443556699" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4dbfc860-8691-4de7-99d5-64b443556699_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_4dbfc860-8691-4de7-99d5-64b443556699" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0millionFixedRateNotesDueSeptember2043InterestEqualTo5.3Member_7dc59760-09ca-4d21-8d2b-e27914f1ce99" xlink:href="cme-20250930.xsd#cme_A750.0millionFixedRateNotesDueSeptember2043InterestEqualTo5.3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:to="loc_cme_A750.0millionFixedRateNotesDueSeptember2043InterestEqualTo5.3Member_7dc59760-09ca-4d21-8d2b-e27914f1ce99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A700.0MillionFixedRateNotesDueJune2048InterestEqualTo4.15MemberDomainDomain_018525c4-c394-4be4-989d-7237cf9ca8bb" xlink:href="cme-20250930.xsd#cme_A700.0MillionFixedRateNotesDueJune2048InterestEqualTo4.15MemberDomainDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:to="loc_cme_A700.0MillionFixedRateNotesDueJune2048InterestEqualTo4.15MemberDomainDomain_018525c4-c394-4be4-989d-7237cf9ca8bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A7500MillionFixedRateNotesDueMarch2032InterestEqualTo265Member_d44a4f5e-6f50-4013-a534-5d6924e7ad02" xlink:href="cme-20250930.xsd#cme_A7500MillionFixedRateNotesDueMarch2032InterestEqualTo265Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:to="loc_cme_A7500MillionFixedRateNotesDueMarch2032InterestEqualTo265Member_d44a4f5e-6f50-4013-a534-5d6924e7ad02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain_bcf537d6-5329-43ef-ab20-cee4449e1d05" xlink:href="cme-20250930.xsd#cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:to="loc_cme_A750MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Domain_bcf537d6-5329-43ef-ab20-cee4449e1d05" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member_6731cea0-5213-46b5-bffc-890a30fa1bf1" xlink:href="cme-20250930.xsd#cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:to="loc_cme_A750.0MillionFixedRateNotesDueMarch2025InterestEqualTo3.00Member_6731cea0-5213-46b5-bffc-890a30fa1bf1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Member_41ef4d04-24e6-4285-8fd7-d94ef0f866eb" xlink:href="cme-20250930.xsd#cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a952e67e-6462-4c0e-8767-d07f3f46b875" xlink:to="loc_cme_A750.0MillionFixedRateNotesDueMarch2030InterestEqualTo4.4Member_41ef4d04-24e6-4285-8fd7-d94ef0f866eb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_3a9d3361-2077-4d55-8264-435c561510ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b7abfd5d-9566-4193-87e5-e0edb8f99d3a" xlink:to="loc_us-gaap_DebtInstrumentFairValue_3a9d3361-2077-4d55-8264-435c561510ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_64b31b2b-2f1a-480a-9395-511819401f85" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b7abfd5d-9566-4193-87e5-e0edb8f99d3a" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_64b31b2b-2f1a-480a-9395-511819401f85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_8d5f0bda-60c8-43e1-be7b-adf6bceba0c9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b7abfd5d-9566-4193-87e5-e0edb8f99d3a" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_8d5f0bda-60c8-43e1-be7b-adf6bceba0c9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cmegroup.com/role/EarningsPerShareNarrativeDetails" xlink:type="simple" xlink:href="cme-20250930.xsd#EarningsPerShareNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cmegroup.com/role/EarningsPerShareNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c902ca30-8be8-4d10-9aed-16190e5bdc6b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_17dbadda-a36b-4da0-98fc-4f85793e148b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c902ca30-8be8-4d10-9aed-16190e5bdc6b" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_17dbadda-a36b-4da0-98fc-4f85793e148b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6c63ae52-2cd5-401f-99e6-fe95dc864aca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_17dbadda-a36b-4da0-98fc-4f85793e148b" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6c63ae52-2cd5-401f-99e6-fe95dc864aca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_6c63ae52-2cd5-401f-99e6-fe95dc864aca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6c63ae52-2cd5-401f-99e6-fe95dc864aca" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_6c63ae52-2cd5-401f-99e6-fe95dc864aca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b1ba5443-1c1d-413d-ac70-a69e5dc8d2c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6c63ae52-2cd5-401f-99e6-fe95dc864aca" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b1ba5443-1c1d-413d-ac70-a69e5dc8d2c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_2371f36f-bec6-41e8-8872-a5a250832f2f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b1ba5443-1c1d-413d-ac70-a69e5dc8d2c7" xlink:to="loc_us-gaap_RestrictedStockMember_2371f36f-bec6-41e8-8872-a5a250832f2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_421775e3-6c5e-4d0e-b103-956c6410c327" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c902ca30-8be8-4d10-9aed-16190e5bdc6b" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_421775e3-6c5e-4d0e-b103-956c6410c327" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
