Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the use in this Amendment No. 1 to Registration Statement No. 333-229578 on Form S-1 of our report dated March 15, 2019 relating to the consolidated financial statements of Avantor, Inc. and subsidiaries appearing in the Prospectus, which is part of this Registration Statement, and to the reference to us under the heading “Experts” in such Prospectus.

/s/ Deloitte & Touche LLP

Philadelphia, Pennsylvania

March 15, 2019