Exhibit 5.1

PILLSBURY WINTHROP SHAW PITTMAN LLP

1200 Seventeenth St. NW

Washington, DC 20036

May 11, 2020

Federal Realty Investment Trust

1626 East Jefferson Street

Rockville, Maryland 20852

Ladies and Gentlemen:

We are acting as counsel for Federal Realty Investment Trust, a Maryland real estate investment trust (the “Company”), in connection with the issuance and sale of (i) $300,000,000 aggregate principal amount of 3.95% Notes due 2024 of the Company (the “2024 Notes”) and (ii) $400,000,000 aggregate principal amount of 3.50% Notes due 2030 of the Company (the “2030 Notes” and, together with the 2024 Notes, collectively, the “Notes”), pursuant to the Underwriting Agreement and related Pricing Agreement, each dated May 7, 2020, between the several underwriters listed in Schedule I to the Pricing Agreement (the “Underwriters”) and the Company (collectively, the “Agreement”). The Notes are being issued under the Indenture dated as of September 1, 1998 between the Company and U.S. Bank National Association (successor trustee to Wachovia Bank, National Association (successor trustee to First Union National Bank)), as Trustee (together with the officers’ certificates dated May 11, 2020 setting forth the terms of the Notes, the “Indenture”).

We have reviewed (a) the Agreement, (b) the Indenture, (c) the Registration Statement on Form S-3 (File No. 333-224701) (the “Registration Statement”) filed by the Company to register the offer and sale of the Notes with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933 (the “Securities Act”), (d) the Prospectus dated May 7, 2018, as supplemented by the Prospectus Supplement dated May 7, 2020, relating to the offer and sale of the Notes (the “Prospectus”), filed by the Company with the Commission pursuant to Rule 424(b)(5) under the Securities Act. We have also reviewed such other agreements, documents, records, certificates and other materials, and have satisfied ourselves as to such other matters, as we have considered relevant or necessary as a basis for this opinion.

In such review, we have assumed the accuracy and completeness of all agreements, documents, records, certificates and other materials submitted to us, the conformity with the originals of all such materials submitted to us as copies (whether or not certified and including facsimiles), the authenticity of the originals of such materials and all materials submitted to us as originals, the genuineness of all signatures and the legal capacity of all natural persons. In delivering this opinion, we have relied, without independent verification, as to factual matters, on certificates and other written or oral statements of governmental and other public officials and of officers and representatives of the Company, the Underwriters and the Trustee.

On the basis of the assumptions and subject to the qualifications and limitations set forth herein, we are of the opinion that the Notes constitute the valid and legally binding obligations of the Company enforceable against the Company in accordance with their terms, except as may be subject to and limited by the effect of (a) applicable bankruptcy, insolvency, reorganization, fraudulent conveyance and other similar laws affecting creditors’ rights generally, (b) general equitable principles (whether considered in a proceeding in equity or at law) and (c) requirements of reasonableness, good faith, materiality and fair dealing and the discretion of the court before which any matter may be brought.

This opinion is limited to the law of the States of New York and Maryland, in each case as in effect on the date hereof.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Company’s Current Report on Form 8-K filed by the Company with the Commission on May 12, 2020 and the incorporation thereof in the Registration Statement and to the use of our name under the captions “Legal Matters” in the Prospectus Supplement. 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 of the Commission promulgated thereunder.

Very truly yours,

/s/ Pillsbury Winthrop Shaw Pittman LLP

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Exhibit 8.1

May 7, 2020

Federal Realty Investment Trust

1626 East Jefferson Street

Rockville, Maryland 20852

Ladies and Gentlemen:

You have requested certain opinions regarding the application of U.S. federal income tax laws to Federal Realty Investment Trust, a Maryland real estate investment trust (the “Company”), in connection with the filing of a prospectus supplement dated May 7, 2020 (the “Prospectus Supplement”) to a prospectus (the “Base Prospectus”) filed as part of a registration statement on Form S-3 (File No. 333-224701, the “Registration Statement,” which term includes the Base Prospectus, Prospectus Supplement, and all documents incorporated and deemed to be incorporated by reference therein) with the Securities and Exchange Commission.

In rendering the following opinions, we have examined such statutes, regulations, records, certificates and other documents as we have considered necessary or appropriate as a basis for such opinions, including the following: (1) the Company’s Registration Statement, (2) the Declaration of Trust of the Company, as amended, restated or supplemented, if applicable (the “Declaration of Trust”) and the Amended and Restated Bylaws of the Company, (3) certain written representations of the Company contained in a letter to us dated as of the date hereof, a copy of which is attached as Schedule 1 hereto, (4) copies of the representative leases entered into by the Company as of the date hereof, and (5) such other documents or information as we have deemed necessary to render the opinions set forth in this letter. In our review, we have assumed, with your consent, that all of the representations and statements set forth in such documents as to factual matters (but not legal conclusions) are true and correct, and all of the obligations imposed by any such documents on the parties thereto, including obligations imposed under the Declaration of Trust, have been or will be performed or satisfied in accordance with their terms. We also have assumed the genuineness of all signatures, the proper execution of all documents, the authenticity of all documents submitted to us as originals, the conformity to originals of documents submitted to us as copies, and the authenticity of the originals from which any copies were made.

Unless facts material to the opinions expressed herein are specifically stated to have been independently established or verified by us, we have relied as to such facts solely upon the representations made by the Company. To the extent that the representations of the Company are with respect to matters set forth in the Internal

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May 7, 2020

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Revenue Code of 1986, as amended (the “Code”) or the regulations promulgated thereunder (the “Treasury Regulations”), we have reviewed with the individuals making such representations the relevant provisions of the Code, the applicable Treasury Regulations and published administrative interpretations thereof. We assume that each representation made by the Company is and will be true, correct and complete, and that all representations that speak in the future, or to the intention, or to the best of belief and knowledge of any person(s) or party(ies) are and will be true, correct and complete as if made without such qualification. Nothing has come to our attention which would cause us to believe that any of such representations are untrue, incorrect or incomplete.

Based upon and subject to the foregoing and to the qualifications below, we are of the opinion that (i) the Company qualified as a real estate investment trust, or REIT, under the Code for each of its taxable years ending after December 31, 1986 and before January 1, 2020; and the Company qualified as a REIT under the Internal Revenue Code of 1954 for each of its taxable years ending before January 1, 1987, (ii) the Company is organized in conformity with the requirements for qualification as a REIT under the Code, and its current method of operation and ownership will enable it to meet the requirements for qualification as a REIT for the current (2020) taxable year and for future taxable years, and (iii) the discussions in (x) the Base Prospectus under the caption “Material Federal Income Tax Considerations,” (y) the Prospectus Supplement under the caption “Additional Material Federal Income Tax Considerations,” and (z) the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 under the captions “Risk Factors–Failure to qualify as a REIT for federal income tax purposes would cause us to be taxed as a corporation, which would substantially reduce funds available for payment of distributions,” “Risk Factors–We may be required to incur additional debt to qualify as a REIT,” “Risk Factors–To maintain our status as a REIT, we limit the amount of shares any one shareholder can own,” and “Risk Factors–U.S. federal tax reform legislation now and in the future could affect REITs, both positively and negatively, in ways that are difficult to anticipate,” which are incorporated by reference into the Registration Statement, to the extent that they discuss matters of law or legal conclusions or purport to describe certain provisions of the federal tax laws, are correct summaries of the matters discussed therein.

The opinions set forth in this letter are based on existing law as contained in the Code, Treasury Regulations (including any Temporary and Proposed Regulations), and interpretations of the foregoing by the Internal Revenue Service and by the courts in effect (or, in case of certain Proposed Regulations, proposed) as of the date hereof, all of which are subject to change, both retroactively or prospectively, and to possibly different interpretations. Moreover, the Company’s ability to achieve and maintain qualification as a REIT depends upon its ability to achieve and maintain certain diversity of stock ownership requirements and, through actual annual operating results, certain requirements under the Code regarding its income, assets and distribution levels. No

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May 7, 2020

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assurance can be given as to whether, for any given taxable year, the actual ownership of the Company’s stock and its actual operating results and distributions satisfy the tests necessary to achieve and maintain its status as a REIT.

The foregoing opinions are limited to the specific matters covered thereby and should not be interpreted to imply the undersigned has offered its opinion on any other matter. We assume no obligation to update the opinions set forth in this letter after the date hereof.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement. The giving of this consent, however, does not constitute an admission that we are “experts” within the meaning of Section 11 of the Securities Act of 1933, as amended (the “Act”), or within the category of persons whose consent is required by Section 7 of the Act.

Very truly yours,

    /s/ PILLSBURY WINTHROP SHAW PITTMAN LLP