Exhibit 99.3

KPMG LLP
Bay Adelaide Centre
333 Bay Street, Suite 4600 Toronto, ON M5H 2S5 Canada
Tel 416-777-8500
Fax 416-777-8818

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement on Form F-10 (No. 333-258939) and Registration Statements on Form S-8 (No. 333-48174, No. 333-148915, No. 333-190121 and No. 333- 224641) of our reports dated March 9, 2023, with respect to the consolidated financial statements of Denison Mines Corp. (the “Company”), which comprise the consolidated statements of financial position as of December 31, 2022 and 2021, the related consolidated statements of income (loss) and comprehensive income (loss), changes in equity and cash flow for each of the years in the two-year period ended December 31, 2022, and the related notes, and the effectiveness of internal control over financial reporting as of December 31, 2022, which reports appear in the Form 6-K of the Entity dated March 9, 2023.

/s/ KPMG LLP

Chartered Professional Accountants, Licensed Public Accountants

March 9, 2023

Toronto, Canada

KPMG LLP is a Canadian limited liability partnership and a member firm of the KPMG network of independent

member firms affiliated with KPMG International Cooperative (“KPMG International”), a Swiss entity.

KPMG Canada provides services to KPMG LLP.