Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in this Registration Statement on Form S-8 of Rubius Therapeutics, Inc. of our report dated April 13, 2018 relating to the financial statements, which appears in Rubius Therapeutics, Inc.’s Amendment No. 2 to the Registration Statement on Form S-1 (No. 333-225840).

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

July 17, 2018