Exhibit 5.1

2000 PENNSYLVANIA AVE., NW WASHINGTON, D.C. 20006-1888   TELEPHONE: 202.887.1500 FACSIMILE: 202.887.0763   WWW.MOFO.COM MORRISON & FOERSTER LLP   NEW YORK, SAN FRANCISCO, LOS ANGELES, PALO ALTO, SACRAMENTO, SAN DIEGO, DENVER, NORTHERN VIRGINIA, WASHINGTON, D.C.   TOKYO, LONDON, BRUSSELS, BEIJING, SHANGHAI, HONG KONG

April 15, 2015

Board of Directors

AutoZone, Inc.

123 South Front Street

Memphis, Tennessee 38103

Re: Registration Statement on Form S-3

Ladies and Gentlemen:

We are acting as special counsel to AutoZone, Inc., a Nevada corporation (the “Company”), in connection with its registration statement on Form S-3 (the “Registration Statement”) filed with the Securities and Exchange Commission relating to the proposed public offering of unsecured debt securities, which may be either senior debt securities or subordinated debt securities (the “Securities”). All of the Securities may be sold from time to time and on a delayed or continuous basis, as set forth in the prospectus which forms a part of the Registration Statement (the “Prospectus”), and as to be set forth in one or more supplements to the Prospectus. This opinion letter is furnished to you at your request to enable you to fulfill the requirements of Item 601(b)(5) of Regulation S-K, 17 C.F.R. § 229.601(b)(5), in connection with the Registration Statement.

For purposes of this opinion letter, we have examined copies of such agreements, instruments and documents as we have deemed an appropriate basis on which to render the opinions hereinafter expressed. In our examination of the aforesaid documents, we have assumed the genuineness of all signatures, the legal capacity of all natural persons, the accuracy and completeness of all documents submitted to us, the authenticity of all original documents, and the conformity to authentic original documents of all documents submitted to us as copies (including telecopies). As to all matters of fact, we have relied on the representations and statements of fact made in the documents so reviewed, and we have not independently established the facts so relied on. This opinion letter is given, and all statements herein are made, in the context of the foregoing.

For purposes of this opinion letter, we have assumed that (i) the issuance, sale, amount and terms of any Securities to be offered from time to time will have been duly authorized and established by action by the Board of Directors of the Company or a duly authorized committee thereof and other proper corporate action of the Company (“Corporate Action”), consistent with the procedures and terms described in the Registration Statement and in accordance with the procedures and terms described in the Registration Statement and in accordance with the Company’s articles of incorporation and bylaws and applicable Nevada corporate law, in a manner that does not violate any law, government or court-imposed order or restriction or agreement or instrument then binding on the Company or otherwise impair the legal or binding nature of the obligations represented by the applicable Securities; (ii) at the time of offer, issuance and sale of any Securities, the Registration

AutoZone, Inc.

April 15, 2015

Page 2

Statement will be effective under the Securities Act of 1933, as amended (the “Act”), and no stop order suspending its effectiveness will have been issued and remain in effect; (iii) any Securities will be issued pursuant to the indenture dated as of August 8, 2003 between the Company and The Bank of New York Mellon Trust Company, N.A. (successor to Bank One Trust Company, N.A.), as trustee (the “Trustee”), filed as Exhibit 4.1 to the Registration Statement and as amended or supplemented from time to time in accordance with its terms (the “Indenture”); (iv) if being sold by the Company, the Securities will be delivered against payment of valid consideration therefor and in accordance with the terms of the applicable Corporate Action authorizing such sale and any underwriting agreement, purchase agreement or other applicable agreement as contemplated by the Registration Statement and/or the applicable supplement to the Prospectus; and (v) the Company will remain a Nevada corporation.

To the extent that the obligations of the Company with respect to the Securities may be dependent upon such matters, we assume for purposes of this opinion that the Trustee is duly organized, validly existing and in good standing under the laws of its jurisdiction of organization; that the Trustee is duly qualified to engage in the activities contemplated by the Indenture; that a Statement of Eligibility of the Trustee on Form T-1 has been properly field with the Securities and Exchange Commission; that the Indenture has been duly authorized, executed and delivered by the Trustee and constitutes the legal, valid and binding obligation of the Trustee enforceable against the Trustee in accordance with its terms; that the Trustee is in compliance, with respect to performance of its obligations under the Indenture, with all applicable laws and regulations; and that the Trustee has the requisite organizational and legal power and authority to perform its obligations under the Indenture.

This opinion letter is based as to matters of law solely on the applicable provisions of the laws of the State of New York (but not including any laws, statutes, ordinances, administrative decisions, rules or regulations of any political subdivision below the state level), as currently in effect. We express no opinion herein as to any other laws, statutes, ordinances, rules, or regulations (and in particular, we express no opinion as to any effect that such other laws, statutes, ordinances, rules, or regulations may have on the opinion expressed herein).

Based upon, subject to and limited by the foregoing, we are of the opinion that the Securities, upon authentication by the Trustee and due execution and delivery on behalf of the Company in accordance with the Indenture and any supplemental indenture or officers’ certificate and company order relating thereto, will constitute valid and binding obligations of the Company.

The opinion expressed above with respect to the valid and binding nature of obligations may be limited by bankruptcy, insolvency, reorganization, receivership, moratorium or other laws affecting creditors’ rights (including, without limitation, the effect of statutory and other law regarding fraudulent conveyances, fraudulent transfers and preferential transfers) and by the exercise of judicial discretion and the application of principles of equity, good faith, fair dealing, reasonableness, conscionability and materiality (regardless of whether the Securities are considered in a proceeding in equity or at law).

AutoZone, Inc.

April 15, 2015

Page 3

This opinion letter has been prepared for your use in connection with the Registration Statement. We assume no obligation to advise you of any changes in the foregoing subsequent to the effective date of the Registration Statement.

We hereby consent to the filing of this opinion letter as Exhibit 5.1 to the Registration Statement and to the reference to this firm under the caption “Legal Matters” in the Prospectus. In giving this consent, we do not thereby admit that we are an “expert” within the meaning of the Act.

Very truly yours,

/s/ Morrison & Foerster LLP