Exhibit 5.1

	San Diego, California 92130 Tel: +1.858.523.5400 Fax: +1.858.523.5450 www.lw.com FIRM / AFFILIATE OFFICES
	Austin Beijing Boston Brussels Century City Chicago Dubai Düsseldorf Frankfurt Hamburg Hong Kong Houston London Los Angeles Madrid	Milan Munich New York Orange County Paris Riyadh San Diego San Francisco Seoul Shanghai Silicon Valley Singapore Tel Aviv Tokyo Washington, D.C.

February 28, 2024

Avidity Biosciences, Inc.

10578 Science Center Drive, Suite 125

San Diego, CA 92121

Re:    Registration Statement on Form S-3; 5,075,304 Shares of Common Stock, Par Value $0.0001 Per Share

To the addressee set forth above:

    We have acted as special counsel to Avidity Biosciences, Inc., a Delaware corporation (the “Company”), in connection with the resale from time to time by the selling securityholders named in the Registration Statement (as defined below) of up to 5,075,304 shares (the “Shares”) of the Company’s common stock, par value $0.0001 per share (the “Common Stock”). The Shares are included in a registration statement on Form S-3 under the Securities Act of 1933, as amended (the “Act”), filed with the U.S. Securities and Exchange Commission (the “Commission”) on February 28, 2024 (the “Registration Statement”).

    This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or the prospectus contained therein, other than as expressly stated herein with respect to the issuance of the Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to the General Corporation Law of the State of Delaware (the “DGCL”), and we express no opinion with respect to any other laws.

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, the issuance of the Shares has been duly authorized by all necessary corporate action of the Company, and the Shares are validly issued, fully paid and non-assessable.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing this opinion as an exhibit to the Registration Statement and to the reference to our firm in the prospectus contained therein under the heading “Legal Matters.” In giving such consent, we do not thereby admit that we are in the category of persons whose

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February 28, 2024

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consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.

Sincerely,

/s/ Latham & Watkins LLP

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