Omnicom Group Inc.
280 Park Avenue
New York, New York 10017

Omnicom Finance Holdings plc
Bankside 3, 90-100 Southwark Street
London, SE1 0SW, United Kingdom

Omnicom Capital Holdings plc
Bankside 3, 90-100 Southwark Street
London, SE1 0SW, United Kingdom

We have acted as counsel for Omnicom Group Inc., a New York corporation (“OGI”), Omnicom Finance Holdings plc, a public limited company organized under the laws of England and Wales (“OFHP”), and Omnicom Capital Holdings plc, a public limited company organized under the laws of England and Wales (“OCHP”), in connection with the authorization of the issuance and sale from time to time, on a delayed basis, (i) by OGI of debt securities of OGI (the “U.S. Debt Securities”), in one or more series, certain of which may be convertible into or exchangeable for Common Stock (as defined below), (ii) by OFHP of debt securities of OFHP (the “OFHP International Debt Securities”), in one or more series, certain of which may be convertible into or exchangeable for Common Stock, (iii) by OCHP of debt securities of OCHP (the “OCHP International Debt Securities”), in one or more series, certain of which may be convertible into or exchangeable for Common Stock, (iv) by OGI of OGI’s guarantee of OFHP’s or OCHP’s, as applicable, obligations in respect of any OFHP International Debt Securities issued by OFHP or any OCHP International Debt Securities issued by OCHP (the “Guarantee”) and (v) by OGI of: (A) shares of common stock, par value $.15 per share, of OGI (the “Common Stock”); (B) shares of preferred stock, par value $1.00 per share, of OGI (the “Preferred Stock”), in one or more series, certain of which may be convertible into or exchangeable for Common Stock; (C) warrants to purchase Common Stock or Preferred Stock (the “Warrants”); and (D) subscription rights to purchase Common Stock, Preferred Stock or Warrants (“Subscription Rights”), in each case, as contemplated by the Registration Statement on Form S-3 to which this opinion has been filed as an exhibit (the “Registration Statement”). The U.S. Debt Securities, the OFHP International Debt Securities, the OCHP International Debt Securities, the Common

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Stock, the Preferred Stock, the Guarantee, the Warrants and the Subscription Rights are collectively referred to herein as the “Securities.” The Securities may be offered and sold from time to time pursuant to Rule 415 under the Securities Act of 1933 (the “Securities Act”).

In connection with the opinions expressed herein, we have examined such documents, records and matters of law as we have deemed relevant or necessary for purposes of this opinion. Based on the foregoing, and subject to the further limitations, qualifications and assumptions set forth herein, we are of the opinion that:

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In rendering the foregoing opinions, we have assumed that: (i) the Registration Statement, and any amendments thereto, will have become effective (and will remain effective at the time of issuance of any Securities thereunder); (ii) a prospectus supplement describing each class or series of Securities offered pursuant to the Registration Statement, to the extent required by applicable law and relevant rules and regulations of the Securities and Exchange Commission (the “Commission”), will be timely filed with the Commission; (iii) the definitive terms of each class or series of Securities will have been established in accordance with the authorizing resolutions adopted by each of OGI’s, OFHP’s, and OCHP’s Board of Directors, as applicable (or an authorized committee thereof), OGI’s restated certificate of incorporation (the “Restated Certificate of Incorporation”) and applicable law; (iv) OFHP, OCHP and OGI, as applicable, will issue and deliver the Securities in the manner contemplated by the Registration Statement and any Securities issuable upon conversion, exchange or exercise of any other Security, will have been authorized and reserved for issuance, in each case within the limits of the then remaining authorized but unreserved and unissued amounts of such Securities; (v) the resolutions authorizing OGI, OFHP and OCHP to issue, offer and sell the Securities will have been adopted by OGI’s, OFHP’s and OCHP’s Board of Directors, as applicable (or an authorized committee thereof), and will be in full force and effect at all times at which the Securities are offered or sold by OFHP, OCHP and OGI, as applicable; (vi) all Securities will be issued in compliance with applicable federal and state securities laws; and (vii) any U.S. Debt Indenture, International Debt Indenture, Warrant Agreement or Subscription Rights Agreement (each as defined below) will be governed by and construed in accordance with the laws of the State of New York.

With respect to any Securities consisting of any series of U.S. Debt Securities, we have further assumed that: (i) such U.S. Debt Securities will have been issued pursuant to an indenture (the “U.S. Debt Indenture”), in a form approved by us, that has been authorized, executed and delivered by OGI and one or more entities selected by OGI to act as trustee (the “U.S. Debt Trustee”), and the U.S. Debt Indenture will have been qualified under the Trust Indenture Act of 1939 (the “TIA”); (ii) all terms of such U.S. Debt Securities not provided for in the U.S. Debt Indenture will have been established in accordance with the provisions of the U.S. Debt Indenture and reflected in appropriate documentation approved by us and, if applicable, executed and delivered by OGI and the U.S. Debt Trustee; and (iii) such U.S. Debt Securities will be

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executed, authenticated, issued and delivered in accordance with the provisions of the U.S. Debt Indenture.

With respect to any Securities consisting of any series of OFHP International Debt Securities or OCHP International Debt Securities, we have further assumed that: (i) such OFHP International Debt Securities or OCHP International Debt Securities and any related Guarantee will have been issued pursuant to an indenture (the “International Debt Indenture”), in a form approved by us, that has been authorized, executed and delivered by OFHP, OCHP, OGI and one or more entities selected by OFHP or OCHP, as applicable, to act as trustee (the “International Debt Trustee”), and the International Debt Indenture will have been qualified under the TIA; (ii) all terms of such OFHP International Debt Securities or OCHP International Debt Securities and any related Guarantee not provided for in the International Debt Indenture will have been established in accordance with the provisions of the International Debt Indenture and reflected in appropriate documentation approved by us and, if applicable, executed and delivered by OFHP, OCHP, OGI and the International Debt Trustee; and (iii) such OFHP International Debt Securities or OCHP International Debt Securities and any related Guarantee will be executed, authenticated, issued and delivered in accordance with the provisions of the International Debt Indenture.

With respect to any Securities consisting of Preferred Stock, we have further assumed that OGI will issue and deliver the shares of the Preferred Stock being issued and delivered after the filing with the Secretary of State of the State of New York of a certificate of amendment to the Restated Certificate of Incorporation, approved by us, establishing the designations, preferences and rights of the class or series of the Preferred Stock being issued and delivered.

With respect to any Securities consisting of Warrants, we have further assumed that: (i) the warrant agreement, approved by us, relating to the Warrants (the “Warrant Agreement”) to be entered into between OGI and an entity selected by OGI to act as the warrant agent (the “Warrant Agent”) will have been authorized, executed and delivered by OGI and the Warrant Agent; and (ii) the Warrants will be authorized, executed and delivered by OGI and the Warrant Agent in accordance with the provisions of the Warrant Agreement.

With respect to any Securities consisting of Subscription Rights, we have further assumed that: (i) the subscription rights agreement, approved by us, relating to the Subscription Rights (the “Subscription Rights Agreement”) to be entered into between OGI and an entity selected by OGI to act as the subscription rights agent (the “Subscription Rights Agent”) will have been authorized, executed and delivered by OGI and the Subscription Rights Agent; and (ii) the Subscription Rights will be authorized, executed and delivered by OGI and the Subscription Rights Agent in accordance with the provisions of the Subscription Rights Agreement.

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For purposes of our opinions set forth in paragraphs 2 and 3, we have further assumed that (i) OFHP is, and will be at the time of issuance of any OFHP International Debt Securities, a public limited company existing and in good standing under the laws of England and Wales, (ii) OCHP is, and will be at the time of issuance of any OCHP International Debt Securities, a public limited company existing and in good standing under the laws of England and Wales, (iii) the OFHP International Debt Securities and the OCHP International Debt Securities (A) will have been authorized by all necessary corporate action of OFHP and OCHP, as applicable, and (B) will have been executed and delivered by OFHP and OCHP, as applicable, under the laws of England and Wales and (iv) the execution, delivery, performance and compliance with the terms and provisions of the OFHP International Debt Securities and the OCHP International Debt Securities by OFHP and OCHP, respectively, do not violate or conflict with the laws of England and Wales or the terms and provisions of OFHP’s or OCHP’s Certificate of Incorporation and Memorandum and Articles of Association, or any rule, regulation, order, decree judgment, instrument or agreement binding upon or applicable to OFHP or OCHP, or OFHP’s or OCHP’s properties.

The opinions set forth in paragraphs 1, 2, 3, 6, 7 and 8 are limited by (i) bankruptcy, insolvency, reorganization, fraudulent transfer and fraudulent conveyance, voidable preference, moratorium or other similar laws, and related regulations and judicial doctrines from time to time in effect relating to or affecting creditors’ rights and remedies generally, and (ii) general equitable principles and public policy considerations, whether such principles and considerations are considered in a proceeding at law or equity.

As to facts material to the opinions and assumptions expressed herein, we have relied upon oral or written statements and representations of officers and other representatives of OGI, OFHP, OCHP and others. The opinions expressed herein are limited to the laws of the State of New York, as currently in effect, and we express no opinion as to the effect of the laws of any other jurisdiction.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to Jones Day under the caption “Validity of Securities” in the prospectus constituting a part of such Registration Statement. In giving such consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

	Very truly yours,

	/s/ Jones Day