Mr. David Cates reports

DENISON ANNOUNCES CLOSING OF TRANSACTION WITH SKYHARBOUR AND FORMATION OF FOUR PROSPECTIVE EXPLORATION JOINT VENTURES PROXIMAL TO WHEELER RIVER

Denison Mines Corp. has closed the previously announced transaction with Skyharbour Resources Ltd. and the formation of four joint ventures consisting of claims previously comprising Skyharbour's Russell Lake uranium project, which is located directly adjacent to Denison's flagship Wheeler River project.

The new joint ventures are designed to drive collaboration between Denison and Skyharbour's technical teams and to accelerate the evaluation of the prospective exploration ground adjacent to and proximal to Wheeler River. Denison will serve as the operator for the Wheeler North and Wheeler River Inliers joint ventures, with ownership interests of 49 per cent and 70 per cent, respectively. Skyharbour will serve as the operator for the Russell Lake (or RL) and Getty East joint ventures, with Denison having ownership interests of 20 per cent and 30 per cent, respectively.

In addition, Denison and Skyharbour have entered into option agreements, which allow Denison to increase its ownership interest in each of the Wheeler North and Getty East joint ventures to up to 70 per cent.

About Denison Mines Corp.

Denison is a leading uranium mining, development and exploration company with interests focused in the Athabasca basin region of Northern Saskatchewan, Canada. Denison has an effective 95-per-cent interest in its flagship Wheeler River uranium project, which is the largest undeveloped uranium project in the infrastructure-rich eastern portion of the Athabasca basin region of Northern Saskatchewan.

In mid-2023, the Phoenix feasibility study was completed for the Phoenix deposit as an ISR mining operation, and an update to the previously prepared 2018 prefeasibility study (PFS) was completed for Wheeler River's Gryphon deposit as a conventional underground mining operation. Based on the respective studies, both deposits have the potential to be competitive with the lowest-cost uranium mining operations in the world. Permitting efforts for the planned Phoenix ISR operation commenced in 2019 and are nearing completion with approval in July, 2025, of the project's EA by the Province of Saskatchewan and conclusion in December, 2025, of the Canadian Nuclear Safety Commission Public Hearing for federal approval of the EA and project construction licence.

Denison's interests in Saskatchewan also include a 22.5-per-cent ownership interest in the McClean Lake joint venture (MLJV), which includes unmined uranium deposits (with mining at McClean North deposit via the MLJV's Sabre mining method having commenced in July, 2025, using the MLJV's Sabre mining method) and the McClean Lake uranium mill (currently utilizing a portion of its licensed capacity to process the ore from the Cigar Lake mine under a toll milling agreement), plus a 25.17-per-cent interest in the Midwest Joint Venture Midwest Main and Midwest A deposits, and a 70.55-per-cent interest in the Tthe Heldeth Tue (THT) and Huskie deposits on the Waterbury Lake property. The Midwest Main, Midwest A, THT and Huskie deposits are located within 20 kilometres of the McClean Lake mill. Taken together, Denison has direct ownership interests in properties covering approximately 457,000 hectares in the Athabasca basin region.

Additionally, through its 50-per-cent ownership of JCU (Canada) Exploration Company Ltd., Denison holds interests in various uranium project joint ventures in Canada, including the Millennium project (JCU, 30.099 per cent), the Kiggavik project (JCU, 33.8118 per cent) and Christie Lake (JCU, 34.4508 per cent).

In 2024, Denison celebrated its 70th year in uranium mining, exploration and development, which began in 1954 with Denison's first acquisition of mining claims in the Elliot Lake region of Northern Ontario.

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