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Exhibit 5.1
July 23, 2021

National Storage Affiliates Trust
8400 East Prentice Avenue, 9th Floor
Greenwood Village, Colorado 80111

Ladies and Gentlemen:

We have acted as counsel to National Storage Affiliates Trust, a Maryland real estate investment trust (the “Company”), in connection with a registration statement on Form S-3 (File No. 333-253663) (the “Registration Statement”) under the Securities Act of 1933, as amended (the "Securities Act"). We are furnishing this letter to you in connection with the offer and sale by the Company of 10,120,000 of the Company's common shares of beneficial interest, par value $0.01 per share (the "Shares"), for issuance pursuant to an Underwriting Agreement, dated July 20, 2021 (the "Underwriting Agreement"), by and among the Company and NSA OP, LP, a Delaware limited partnership (the "Operating Partnership"), and Morgan Stanley & Co. LLC, Citigroup Global Markets Inc. and BofA Securities, Inc., as representatives of the several underwriters named in Schedule A thereto (the "Underwriters").

In rendering the opinion expressed below, we have examined and relied upon originals or copies, certified or otherwise identified to our satisfaction, of such corporate records, documents, certificates and other instruments as in our judgment are necessary or appropriate. As to factual matters relevant to the opinion set forth below, we have, with your permission, relied upon certificates of officers of the Company and public officials.

Based on the foregoing, and such other examination of law and fact as we have deemed necessary, we are of the opinion that following the (i) issuance of the Shares pursuant to the terms of the Underwriting Agreement and (ii) receipt by the Company of the consideration for the Shares specified in the resolutions of the board of trustees of the Company (the "Board") and the pricing committee of the Board, the Shares will be legally issued, fully paid, and nonassessable.

This foregoing opinion is based as to matters of law solely on the applicable provisions of the Maryland REIT Law, as amended, currently in effect. We express no opinion herein as to any other laws, statutes, ordinances, rules, or regulations.

We hereby consent to the filing of this opinion with the Securities and Exchange Commission (the “SEC”) as an exhibit to a Current Report on Form 8-K that shall be incorporated by reference into the Registration Statement and to the reference to us under the caption "Legal Matters" in the prospectus supplement which is part of the Registration Statement. In giving such 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 of the SEC thereunder.

Very truly yours,
/s/ Clifford Chance US LLP