UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

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Marsh & McLennan Companies, Inc.

(Name of Registrant as Specified in its Charter)

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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on May 21, 2020. Meeting Information MARSH & McLENNAN COMPANIES, INC. Meeting Type: Annual Meeting For holders as of: March 23, 2020 Date: May 21, 2020 Time: 10:00 A.M. EDT Location: Marsh & McLennan Companies, Inc. 1166 Avenue of the Americas New York, NY 10036 You are receiving this communication because you hold shares in the company named above. MARSH & McLENNAN COMPANIES, INC. 1166 AVENUE OF THE AMERICAS This is not a ballot. You cannot use this notice to vote these NEW YORK, NY 10036 shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. P33762 See proxy the materials reverse and side voting of this instructions. notice to obtain E95204 -

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: NOTICE AND PROXY STATEMENT ANNUAL REPORT How to View Online: Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET: www.proxyvote.com 2) BY TELEPHONE: 1-800-579-1639 3) BY E-MAIL*: sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) in the subject line. Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 7, 2020 to facilitate timely delivery. How To Vote Please Choose One of the Following Voting Methods Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) available and follow the instructions. P33762 Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card. - Vote In Person: Many stockholder meetings have attendance requirements including, but not limited to, the possession E95205 of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares.

Voting Items The Board of Directors recommends you vote FOR the following directors: The Board of Directors recommends you vote FOR the Item 1 Election of Directors following proposals: Item 2 Advisory (Nonbinding) Vote to Approve Named 1a. Anthony K. Anderson Executive Officer Compensation 1b. Oscar Fanjul Item 3 Ratification of Selection of Independent Registered Public Accounting Firm 1c. Daniel S. Glaser Item 4 Approval of the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan 1d. H. Edward Hanway 1e. Deborah C. Hopkins 1f. Tamara Ingram 1g. Jane H. Lute 1h. Steven A. Mills 1i. Bruce P. Nolop 1j. Marc D. Oken 1k. Morton O. Schapiro 1l. Lloyd M. Yates 1m. R. David Yost - P33762 E95206

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