Omnicom Group Inc. in connection with the issuance and sale of $800,000,000 aggregate principal amount of 2.600% Senior Notes due 2031 of OGI (the "Notes"), pursuant to the Underwriting Agreement, dated April 28, 2021, by and among OGI, Barclays Capital Inc., Citigroup Global Markets Inc., and Wells Fargo Securities, LLC, acting as representatives of the several underwriters named therein. The Notes are being issued pursuant to an indenture, dated as of February 21, 2020, by and between OGI and Deutsche Bank Trust Company Americas, as trustee (the "Trustee"), as supplemented by the Third Supplemental Indenture, dated as of May 3, 2021, by and between OGI and the Trustee (as so supplemented, the "Indenture"). In connection with the opinion expressed herein, company have examined such documents, records and matters of law as company have deemed relevant or necessary for purposes of such opinion. Based on the foregoing, and subject to the further limitations, qualifications and assumptions set forth herein, company are of the opinion that the Notes constitute valid and binding obligations of OGI.