December 5, 2019

John Pietrowicz
Chief Financial Officer
CME Group, Inc.
20 South Wacker Drive
Chicago, IL 60606

       Re: CME Group, Inc.
           Form 10-K for the Fiscal Year Ended December 31, 2018
           Filed February 28, 2019
           File No. 001-31553

Dear Mr. Pietrowicz:

       We have reviewed your filing and have the following comments. In some of
our
comments, we may ask you to provide us with information so we may better
understand your
disclosure.

       Please respond to these comments within ten business days by providing
the requested
information or advise us as soon as possible when you will respond. If you do
not believe our
comments apply to your facts and circumstances, please tell us why in your
response.

       After reviewing your response to these comments, we may have additional
comments.

Form 10-K for the Fiscal Year Ended December 31, 2018

Notes to Consolidated Financial Statements
3. Business Combinations, page 62

1.    We note that you completed the acquisition of NEX Group plc (NEX) on
November 2,
      2018 and, as disclosed in Exhibit 99.1 in your Form 8-K filed on November
8, 2018, that
      the pro forma 2017 annual revenues would be $4.3 billion giving effect to
the acquisition,
      compared to your actual 2017 GAAP revenues of $3.6 billion. However, it
is not clear
      where you have disclosed all information required by ASC 805 for this
acquisition, such
      as the amounts of post-acquisition revenues and earnings or supplemental
pro forma
      revenues and earnings required by ASC 805-10-50-2(h). In your future
filings, please
      revise to disclose all information required by ASC 805-10-50 or tell us
why you do not
      think it is required.
 John Pietrowicz
CME Group, Inc.
December 5, 2019
Page 2
2.       Please provide us with a summary of the income significance test
pursuant to Rule 1-
         02(w) of Regulation S-X prepared in your determination of whether
audited financial
         statements of NEX and full pro forma financial information should be
provided pursuant
         to Rule 3-05 and Article 11 of Regulation S-X, respectively.
        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

       You may contact Robert Klein at 202-551-3847 or Hugh West, Branch Chief,
at 202-
551-3872 if you have questions regarding comments on the financial statements
and related
matters.



FirstName LastNameJohn Pietrowicz                           Sincerely,
Comapany NameCME Group, Inc.
                                                            Division of
Corporation Finance
December 5, 2019 Page 2                                     Office of Finance
FirstName LastName