Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption “Experts” and to the use of our report dated March 26, 2021 (except for Note 14(b), as to which the date is June 14, 2021), in Amendment No. 2 to the Registration Statement (Form S-1 No. 333-256601) and related Prospectus of Cyteir Therapeutics, Inc. dated June 14, 2021 for the registration of shares of its common stock.

/s/ Ernst & Young LLP

Boston, Massachusetts

June 14, 2021