Exhibit 23.1

Independent Registered Public Accounting Firm’s Consent

We consent to the inclusion in this Registration Statement of GP-Act III Acquisition Corp. (the “Company”) on Form S-1 of our report dated February 1, 2021, which includes an explanatory paragraph as to the Company’s ability to continue as a going concern, with respect to our audit of the financial statements of GP-Act III Acquisition Corp. (formerly known as GP Investments Acquisition Corp. II) as of November 30, 2020 and for the period from November 23, 2020 (inception) through November 30, 2020, which report appears in the Prospectus, which is part of this Registration Statement. We also consent to the reference to our Firm under the heading “Experts” in such Prospectus.

/s/ Marcum llp

Marcum llp

New York, NY

March 3, 2021