Executive Change · Reg FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 29, 2021 OMNICOM GROUP INC. (Exact Name of Registrant as Specified in its Charter) New York 1-10551 13-1514814 (State or other jurisdiction of incorporation) (Commission File Number) (IRS Employer Identification No.) 280 Park Avenue , New York , NY 10017 (Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code: (212) 415-3600 Not Applicable (Former name or former address, if changed since last report) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions ( see General Instruction A.2. below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Title of each class Trading Symbol Name of each exchange on which registered Common Stock, par value $0.15 per share OMC New York Stock Exchange 0.800% Senior Notes due 2027 OMC/27 New York Stock Exchange 1.400% Senior Notes due 2031 OMC/31 New York Stock Exchange Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. On October 29, 2021, the Board of Directors of Omnicom Group Inc. (the “Company”) appointed Daryl Simm as President and Chief Operating Officer of the Company, effective November 1, 2021. Mr. Simm, age 60, previously served as Chief Executive Officer of Omnicom Media Group (OMG) for more than two decades, having joined the Company in 1998. Before joining Omnicom, Mr. Simm started his career at Procter & Gamble, where he was General Manager of P&G Productions and VP of Worldwide Media. Item 7.01. Regulation FD Disclosure. A copy of the press release issued by the Company on November 1, 2021 announcing the new role for Mr. Simm and another management change is furnished as Exhibit 99.1 hereto and is incorporated by reference herein. Item 9.01. Financial Statements and Exhibits. Exhibit Number Description 99.1   Press release, dated November 1, 2021.   104 The cover page from this Current Report on Form 8-K, formatted in Inline XBRL. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.   Omnicom Group Inc. Date: November 1, 2021 By: /s/ Michael J. O’Brien Name: Michael J. O’Brien Title: Executive Vice President, General Counsel and Secretary