Exhibit 5.1

[LETTERHEAD OF SKADDEN, ARPS, SLATE, MEAGHER & FLOM]

December 12, 2011

Devon Energy Corporation

20 North Broadway

Oklahoma City, Oklahoma 73102-8260

Re: Devon Energy Corporation

Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as special counsel to Devon Energy Corporation, a Delaware corporation (the “Company”), in connection with the automatic shelf registration statement on Form S-3, to be filed on the date hereof by the Company (the “Registration Statement”) with the U.S. Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”). The Registration Statement relates to, among other things, the issuance and sale from time to time by the Company, pursuant to Rule 415 of the General Rules and Regulations under the Securities Act (the “Rules and Regulations”), of the following securities of the Company: (i) shares of common stock, par value $0.01 per share (the “Common Stock”); (ii) shares of preferred stock, par value $0.01 per share (the “Preferred Stock”), which may be issued in one or more series; (iii) senior debt securities of the Company (the “Senior Debt Securities”), which may be issued in one or more series under an indenture entered into by and between the Company and UMB Bank, National Association, as trustee (the “Senior Trustee”), dated as of July 12, 2011 (the “Base Indenture” and, together with any officers’ certificate, board resolution or supplement thereto establishing the terms of any series of the Senior Debt Securities, the “Senior Indenture”); (iv) subordinated debt securities of the Company (the “Subordinated Debt Securities” and, together with the Senior Debt Securities, the “Debt Securities”), which may be issued in one or more series under an indenture proposed to be entered into by and between the Company and a trustee that will be appointed prior to the issuance of any Subordinated Debt Securities (the “Subordinated Trustee” and, together with the Senior Trustee, the “Trustees” and each a “Trustee”), the form of which is being filed as an exhibit to the Registration Statement (the “Subordinated Base Indenture” and, together with any officers’ certificate, board resolution or supplement thereto establishing the terms of any series of the Subordinated Debt Securities, the “Subordinated Indenture”) and (v) such indeterminate number of

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shares of Common Stock or Preferred Stock and amount of Debt Securities, as may be issued upon conversion, exchange, settlement or exercise of any Preferred Stock or Debt Securities, including such shares of Common Stock or Preferred Stock as may be issued pursuant to anti-dilution adjustments, in amounts, at prices and on terms to be determined at the time of the offering (collectively, “Indeterminate Securities”). The Common Stock, Preferred Stock, Debt Securities and Indeterminate Securities are collectively referred to herein as the “Offered Securities.” The Senior Indenture and the Subordinated Indenture are collectively referred to herein as the “Indentures” and each an “Indenture.”

This opinion is being furnished in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

In rendering the opinions stated herein, we have examined and relied upon the following:

(i) the Registration Statement;

(ii) a copy of the Amended and Restated Certificate of Incorporation of the Company, dated June 8, 2011, as certified by the Secretary of State of the State of Delaware as of December 8, 2011, and as certified by Carla Brockman, Secretary of the Company (the “Certificate of Incorporation”);

(iii) a copy of the Bylaws of the Company, as currently in effect and as certified by Carla Brockman, Secretary of the Company (the “Bylaws”);

(iv) copies of certain resolutions of the Offering Committee of the board of directors of the Company (the “Board of Directors”) adopted on July 5, 2011, relating to the approval of the Senior Base Indenture and related matters, as certified by Carla Brockman, Secretary of the Company;

(v) copies of certain resolutions of the Board of Directors adopted on November 30, 2011, relating to the registration of the Offered Securities, approval of the Subordinated Base Indenture and related matters, as certified by Carla Brockman, Secretary of the Company;

(vi) the Senior Base Indenture;

(vii) the form of the Subordinated Base Indenture; and

(viii) the Statement of Eligibility and Qualification on Form T-1 under the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”), of the Senior Trustee, which is filed as an exhibit to the Registration Statement.

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We have also examined originals or copies, certified or otherwise identified to our satisfaction, of such records of the Company, and such agreements, certificates and receipts of public officials, certificates of officers or other representatives of the Company and others, and such other documents, certificates and records as we have deemed necessary or appropriate as a basis for the opinions stated below.

In our examination, we have assumed the genuineness of all signatures including endorsements, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as facsimile, electronic, certified, conformed or photostatic copies, and the authenticity of the originals of such copies. As to any facts relevant to the opinions stated herein that we did not independently establish or verify, we have relied upon oral or written statements and representations of officers and other representatives of the Company and others and of public officials.

In making our examination of documents executed or to be executed, we have assumed that each of the parties thereto, other than the Company, has been duly organized and is validly existing in good standing, had or will have the power, corporate or other, to enter into and perform all obligations thereunder and have also assumed the due authorization by all requisite action, corporate or other, and the execution and delivery by such parties of such documents, and the validity and binding effect thereof on such parties.

We do not express any opinion with respect to the laws of any jurisdiction other than (i) the General Corporation Law of the State of Delaware (the “DGCL”) and (ii) the laws of the State of New York that, in our experience, are normally applicable to transactions of the type contemplated by the Registration Statement and, to the extent that judicial or regulatory orders or decrees or consents, approvals, licenses, authorizations, validations, filings, recordings or registrations with governmental authorities are relevant, to those required under such laws (all of the foregoing being referred to as “Opined on Law”), or as to the effect of any such non-Opined on Law on the opinions stated herein. The Offered Securities may be issued from time to time on a delayed or continuous basis, and this opinion is limited to the laws, including the rules and regulations, as in effect on the date hereof, which laws are subject to change with possible retroactive effect.

Based upon the foregoing and subject to the limitations, qualifications, exceptions and assumptions stated herein, we are of the opinion that:

1. With respect to any shares of Common Stock offered by the Company pursuant to the Registration Statement (the “Offered Common Stock”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Securities Act; (ii) an appropriate prospectus supplement with respect to the Offered Common Stock has been prepared, delivered and filed in compliance with the Securities Act and the applicable Rules and Regulations; (iii) if the Offered Common Stock is to be sold or otherwise distributed pursuant to a firm commitment underwritten offering, the underwriting agreement or such other agreement with respect to the Offered Common Stock has been duly authorized, executed and delivered by the Company and the other parties thereto; (iv) the Board of Directors, including any appropriate committee appointed thereby, and the appropriate officers of the Company have taken all

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necessary corporate action to approve the issuance and sale of the Offered Common Stock and related matters; (v) the terms of the issuance and sale of the Offered Common Stock have been duly established and are in conformity with the Certificate of Incorporation and the Bylaws so as not to violate any applicable law, the Certificate of Incorporation or the Bylaws or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company; (vi) if certificated, certificates in the form required under the DGCL representing the shares of Offered Common Stock have been duly executed and countersigned; and (vii) the shares of Offered Common Stock are registered in the Company’s share registry and delivered upon payment of the agreed-upon consideration therefor, the shares of Offered Common Stock (including any Offered Common Stock duly issued upon conversion, exchange or exercise of any preferred stock or debt securities), when issued and sold or otherwise distributed in accordance with the applicable underwriting agreement, if any, or any other duly authorized, executed and delivered valid and binding agreement, will be duly authorized, validly issued, fully paid and nonassessable, provided that the consideration therefor is not less than the par value per share of Common Stock.

2. With respect to the shares of any series of Preferred Stock offered by the Company pursuant to the Registration Statement (the “Offered Preferred Stock”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Securities Act; (ii) an appropriate prospectus supplement with respect to the Offered Preferred Stock has been prepared, delivered and filed in compliance with the Securities Act and the applicable Rules and Regulations; (iii) if the Offered Preferred Stock is to be sold or otherwise distributed pursuant to a firm commitment underwritten offering, the underwriting agreement or such other agreement with respect to the Offered Preferred Stock has been duly authorized, executed and delivered by the Company and the other parties thereto; (iv) the Board of Directors, including any appropriate committee appointed thereby, and the appropriate officers of the Company have taken all necessary corporate action to approve the issuance, sale and terms of the Offered Preferred Stock and related matters, including the adoption of a Certificate of Designation for the Offered Preferred Stock in accordance with the applicable provisions of the DGCL (the “Certificate of Designation”); (v) the filing of the Certificate of Designation with the Secretary of State of the State of Delaware, in the form to be filed on a Current Report on Form 8-K or other applicable periodic report and as described in the Registration Statement or any prospectus supplement relating thereto, has duly occurred; (vi) the terms of the Offered Preferred Stock and of their issuance and sale have been duly established and are in conformity with the Certificate of Incorporation, including the Certificate of Designation relating to the Offered Preferred Stock, and the Bylaws so as not to violate any applicable law, the Certificate of Incorporation, including the Certificate of Designation relating to the Offered Preferred Stock, or the Bylaws or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company; (vii) if certificated, certificates in the form required under the DGCL representing the shares of Offered Preferred Stock have been duly executed and countersigned; and (viii) the shares of Offered Preferred Stock are registered in the Company’s share registry and delivered upon payment of the agreed-upon consideration

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therefor, the shares of Offered Preferred Stock (including any Offered Preferred Stock duly issued upon conversion, exchange or exercise of any other preferred stock or debt securities), when issued and sold or otherwise distributed in accordance with the applicable underwriting agreement, if any, or any other duly authorized, executed and delivered valid and binding agreement, will be duly authorized, validly issued, fully paid and nonassessable, provided that the consideration therefor is not less than the par value per share of Preferred Stock.

3. With respect to any series of Debt Securities offered by the Company pursuant to the Registration Statement (the “Offered Debt Securities”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Securities Act and the applicable Indenture for such Debt Securities has been qualified under the Trust Indenture Act; (ii) an appropriate prospectus supplement with respect to the Offered Debt Securities has been prepared, delivered and filed in compliance with the Securities Act and the applicable Rules and Regulations; (iii) if the Offered Debt Securities are to be sold or otherwise distributed pursuant to a firm commitment underwritten offering, the underwriting agreement or such other agreement with respect to the Offered Debt Securities has been duly authorized, executed and delivered by the Company and the other parties thereto; (iv) the applicable Indenture for such Offered Debt Securities has been duly authorized, executed and delivered by the Company and the other parties thereto; (v) the Board of Directors, including any appropriate committee appointed thereby, and the appropriate officers of the Company have taken all necessary corporate action to approve the issuance, sale and terms of the Offered Debt Securities and related matters in conformity with the Indenture to be entered into in connection with the issuance of such Offered Debt Securities; (vi) the terms of the Offered Debt Securities and of their issuance and sale have been duly established in conformity with the applicable Indenture so as not to violate any applicable law, the Certificate of Incorporation or the Bylaws or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company; (vii) with respect to the Subordinated Debt Securities, the Statement of Eligibility and Qualification on Form T-1 under the Trust Indenture Act of the Subordinated Trustee has been filed as required by the Trust Indenture Act and (viii) the certificates evidencing the Offered Debt Securities, in the form to be filed on a Current Report on Form 8-K or other applicable periodic report in the manner contemplated by the Registration Statement or any prospectus supplement relating thereto, have been duly executed and authenticated in accordance with the provisions of the applicable Indenture to be entered into in connection with the issuance of such Offered Debt Securities and duly issued in accordance with the applicable Indenture and the applicable underwriting agreement, if any, or any other duly authorized, executed and delivered valid and binding purchase or agency agreement, the Offered Debt Securities (including any Debt Securities duly issued upon conversion, exchange or exercise of any preferred stock or other debt securities), when issued and sold or otherwise distributed in accordance with the applicable Indenture and the applicable underwriting agreement, if any, or any other duly authorized, executed and delivered valid and binding agreement, will constitute valid and binding obligations of the Company, entitled to the benefits of the applicable Indenture and enforceable against the Company in accordance with their respective terms under the laws of the State of New York, except to the extent that enforcement thereof may be limited by (a) bankruptcy, insolvency, reorganization,

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fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to creditors’ rights generally, (b) general principles of equity (regardless of whether enforceability is considered in a proceeding at law or in equity), (c) public policy considerations which may limit the rights of parties to obtain remedies, (d) waivers of any usury defense contained in the Indentures or the Offered Debt Securities which may be unenforceable and (e) governmental authority to limit, delay or prohibit the making of payments outside the United States or in foreign currencies, currency units or composite currencies.

The opinions stated herein are subject to the following qualifications:

(a) we do not express any opinion as to the enforceability of any rights to indemnification or contribution that may be violative of the public policy underlying any law, rule or regulation (including any federal or state securities law, rule or regulation);

(b) we do not express any opinion as to the enforceability of any provision of any document purporting to prohibit, restrict or condition the assignment of rights under such document to the extent such restriction on assignability is governed by the Uniform Commercial Code;

(c) to the extent any opinion relates to the enforceability of the choice of New York law and choice of New York forum provisions of any agreement or instrument, our opinion is rendered in reliance upon N.Y. Gen. Oblig. Law §§5-1401, 5-1402 (McKinney 2001) and N.Y. C.P.L.R. 327(b) (McKinney 2001) and is subject to the qualification that such enforceability may be limited by public policy considerations; and

(d) with respect to the enforceability of all obligations under the Indentures and any Offered Debt Securities not denominated in U.S. dollars, we note that a U.S. federal court would award a judgment only in U.S. dollars and that a judgment of a court in the State of New York rendered in a currency other than the U.S. dollar would be converted into U.S. dollars at the rate of exchange prevailing on the date of entry of such judgment. Our opinion is subject to possible judicial action giving effect to governmental actions or foreign laws affecting creditors’ rights, and we do not express any opinion as to the enforceability of the provisions of the Indentures or any Offered Debt Securities providing for indemnity by any party thereto against any loss in obtaining the currency due to such party under any of the Indentures or Offered Debt Securities issued thereunder from a court judgment in another currency.

In addition, in rendering the foregoing opinions we have assumed that:

(a) the Subordinated Base Indenture will be in substantially the form reviewed by us, and that any Debt Securities that may be issued will be manually authenticated by duly authorized officers of its respective Trustee; and

(b) except to the extent expressly stated in the opinions contained herein with respect to the Company, the terms of the Offered Securities will have been established so as not to, and that the execution and delivery by the Company of, and the performance of its obligations under, the Indentures and the Offered Securities, will not (i) violate any law,

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rule or regulation to which the Company or its property is subject or (ii) require the consent, approval, licensing or authorization of, or any filing, recording or registration with, any governmental authority under any law, rule or regulation of any jurisdiction.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement. We also hereby consent to the reference to our firm under the heading “Legal Matters” in the prospectus which forms a part of the Registration Statement. In giving this consent, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the Rules and Regulations. This opinion is expressed as of the date hereof unless otherwise expressly stated, and we disclaim any undertaking to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable laws.

Very truly yours,

/s/ Skadden, Arps, Slate, Meagher & Flom LLP