UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of June 2021

Commission File Number 001-38810

STEALTH BIOTHERAPEUTICS CORP

(Translation of registrant’s name into English)

Stealth BioTherapeutics Corp

c/o Intertrust Corporate Services (Cayman) Limited

One Nexus Way, Camana Bay

Grand Cayman

KY1-9005 Cayman Islands

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

FORM 20-F  ☒    FORM 40-F  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ☐

Annual General Meeting

Attached hereto and incorporated by reference herein are the following materials related to the Annual General Meeting of Shareholders of Stealth BioTherapeutics Corp to be held on July 14, 2021: (i) Proxy Statement, (ii) Notice of Annual General Meeting and (iii) Form of Proxy.

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EXHIBIT INDEX

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

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