Denison & Ya’thi Néné Lands and Resources Announce Signing of the Nuhenéné Benefit Agreement with Three First Nations and Four Municipalities

PRESS RELEASE

Denison & Ya’thi Néné Lands and Resources Announce

Signing of the Nuhenéné Benefit Agreement

with Three First Nations and Four Municipalities

Saskatoon, SK – December 1, 20 25. Denison Mines Corp. (“Denison” or the “Company”)

(TSX: DML, NYSE American: DNN) and the Ya'thi Néné Land and Resource Office (“YNLR”)

are pleased to announce the signing of the Nuhenéné Benefit Agreement (“Agreement”), which

is a regional mutual benefits agreement between Denison and the Hatchet Lake Denesułiné First

Nation, Black Lake Denesułiné First Nation, Fond du Lac Denesułiné First Nation, the Northern

Hamlet of Stony Rapids, the Northern Settlement of Uranium City, the Northern Settlement of

Wollaston Lake, the Northern Settlement of Camsell Portage (collectively the “ Athabasca

Communities”), and YNLR. The Agreement provides the Athabasca Communities’ consent to

and support for the development and operation of Denison’s majority owned and operated

Wheeler River Project and Waterbury Lake Project, and also includes Denison’s minority interest

in the Midwest Project (25.77% Denison owned), and the operating McClean Lake Project (22.5%

Denison owned), all of which are located in northern Saskatchewan (collectively the “Projects”).

David Cates, President and CEO of Denison commented, “The execution of the Nuhenéné

Benefit Agreement marks another significant milestone for Denison and the Wheeler River

Project, which is in the final stages of the Federal approval process for the Environmental

Assessment and construction license for the planned Phoenix i n-situ recovery uranium

mine. Negotiations of the Agreement began following the signing of an exploration

agreement between Denison and the Athabasca Communities in 2022. Since that time, our

team has focused its extensive engagement effor ts towards cultivating a strong and

enduring relationship built on trust and mutual respect. We are honoured to sign this

agreement, and extend our sincere appreciation to the leadership of the Athabasca

Communities, the YNLR board members involved in the negotiation process, and the

numerous community members and support staff that have contributed to our

engagement activities over the last several years.”

“This agreement shows what we can achieve when we put our people and our land at the

centre of every decision,” said Chief Bart Tsannie of Hatchet Lake Denesųłiné First Nation. “We

expect responsible development, and we expect real benefits for our communities. This

agreement delivers on that.”

Chief Coreen Sayazie of Black Lake Denesųłiné First Nation commented, “YNLR led these

negotiations with dedication, and we are proud of all who contributed to this work. Denison

came to the table with honesty and integrity, and that helped us reach a fair and meaningful

agreement. This agreement is the result of many voices working together for the

Athabasca region, and it is a major achievement for all our communities.”

“As Chief of Fond du Lac Denesųłiné First Nation, I believe this partnership will help build

long-term prosperity for the Athabasca region,” said Chief Ronnie Augier. “We believe in

sustainable development, but also in strong protection of the land we depend on.

Balancing these two priorities is central to Fond du Lac’s and YNLR’s work, and this

agreement supports that balance for our children and future generations.”

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The C

hairperson of Wollaston Lake Post, Terri Daniels, commented, “This agreement creates

real opportunities for our people - good jobs, strong training programs, and space for our

local businesses to grow. These benefits will help our members participate fully in the

northern economy.”

Mayor Daniel Powder of Stony Rapids, stated, “This agreement reflects years of hard work to

protect our rights, our land, and our way of life. It is a positive step that honours our values

while creating opportunities for our people to benefit from activity in our territory.”

“Independent environmental monitoring has always been a priority for our communities,”

said Uranium City Chairperson, Duane Larocque. “This agreement strengthens our role in

overseeing the land, the water, and the wildlife. It gives us a clear role in making sure the

activities are carried out with respect and transparency.”

Chairperson Claire Larocque of Camsell Portage said, “Our seven Athabasca communities

have worked side by side for many years, and this agreement reflects the strength of that

unity. When we stand together, we open the door to real opportunities and positive

outcomes for our region.”

“Our ongoing work with Denison has shown their readiness to listen, collaborate, and

support the priorities of Athabasca residents,” said Mary Denechezhe, YNLR Board Chair.

“This agreement builds on that foundation and creates meaningful opportunities for our

communities while supporting responsible development.”

Figur

e 1: Map of Nuhenéné Benefits Agreement Projects

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N

uhenéné Benefit Agreement

The Agreement acknowledges that the Projects are located within the Nuhenéné Traditional Land

of the Athabasca Denesułiné (see Figure 1) and provides Denison with the Athabasca

Communities’ consent and support to advance the Projects. Amongst other key commitments,

the Agreement provides the Athabasca Communities and its members an important role in

environmental oversight, with specific recognition and support for the protection of the Woodland

Caribou and for surface water monitoring. The Agreement also commits to the sharing of benefits

from the successful operation of the Projects — including community investment, business

opportunities, employment and training opportunities, and financial compensation.

Overall, the Agreement describes a jointly held vision for the future that reflects a mutual

commitment to maintain an open, respectful, and cooperative relationship between Denison and

the Athabasca Communities. Importantly, the Agreement defines the characteristics of the

positive legacy that will be associated with the sustainable development of the Projects.

A

bout Denison

D

enison 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% 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 Pre-Feasibility 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 commencement in October 2025 of the

Canadian Nuclear Safety Commission Hearings for Federal approval of the EA and project

construction license. The Hearing is scheduled to continue and be concluded during the week of

December 8, 2025.

Denison's interests in Saskatchewan also include a 22.5% 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% interest in the Midwest Joint Venture Midwest Main and Midwest A

deposits, and a 70.55% interest in the Tthe Heldeth Túé ('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 ~384,000 hectares in the Athabasca Basin region.

Additionally, through its 50% ownership of JCU (Canada) Exploration Company, Limited ('JCU'),

Denison holds interests in various uranium project joint ventures in Canada, including the

Millennium project (JCU, 30.099%), the Kiggavik project (JCU, 33.8118% ) and Christie Lake

(JCU, 34.4508%).

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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(416) 979-1991 ext. 362

(416) 979-1991 ext. 358

@DenisonMinesCo

For more information about Denison, please contact

David Cates

President and Chief Executive Officer

Geoff Smith

Vice President Corporate Development & Commercial

Follow Denison on X

About YNLR and the Athabasca Communities of Nuhenéné

Y

NLR is a non-profit organization owned by the seven Athabasca Basin communities: Hatchet

Lake First Nation, Black Lake First Nation, Fond du Lac First Nation, and the northern

municipalities of Stony Rapids, Wollaston Lake, Uranium City, and Camsell Portage. Together,

these communities represent the heart of Nuhenéné, the vast and culturally significant Traditional

Land of the Athabasca Denesułiné, encompassing remote lakes, caribou ranges, traplines, travel

routes, and harvesting areas that continue to sustain the people in this territory.

YNLR was established in 2016 following the signing of the Ya’thi Néné Collaboration Agreement

between the Athabasca communities and uranium producers Cameco and Orano. The

organization was created to ensure that the voices, rights, and long-term interests of Athabasca

residents are meaningfully represented in decisions affecting their lands, waters, and

communities.

YNLR works to protect the environmental, social, economic, and cultural well -being of the

Athabasca region, guided by the knowledge, traditions, and aspirations of the Denesułiné people.

The organization serves as a regional steward and trusted partner, working closely with industry

and government to ensure responsible development within Nuhenéné. Through Indigenous -led

land stewardship, rigorous environmental monitoring, community engagement, and support for

education, training, and employment, YNLR strives to uphold a balanced approach that protects

the land and water for traditional use while promoting sustainable development and economic

opportunities for Athabasca residents.

For more information about YNLR, please contact

G

arrett Schmidt (306) 370

-3358

Executive Director, YNLR

K

athy Hay (306) 270

-4083

Manager of Corporate Affairs, YNLR

Fol

low YNLR on Facebook, Instagram, LinkedIn @YathiNene

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Certain information contained in this news release constitutes ‘forward- looking information’, within the

meaning of the applicable United States and Canadian legislation, concerning the business, operations and

financial performance and condition of Deniso n. Generally, these forward -looking statements can be

identified by the use of forward- looking terminology such as ‘potential’, ‘plans’, ‘expects’, ‘budget’,

‘scheduled’, ‘estimates’, ‘forecasts’, ‘intends’, ‘anticipates’, or ‘believes’, or the negatives and/or variations

of such words and phrases, or state that certain actions, events or results ‘may’, ‘could’, ‘would’, ‘might’ or

‘will’ ‘be taken’, ‘occur’ or ‘be achieved’.

In particular, this news release contains forward -looking information pertaining to Denison's current

intentions and objectives with respect to, and commitments set forth in the Nuhenéné Benefit Agreement;

development and expansion plans and objectives for the Projects ; and expectations regarding its joint

venture ownership interests and the continuity of its agreements with its partners and third parties.

Forward looking statements are based on the opinions and estimates of management as of the date such

statements are made, and they are subject to known and unknown risks, uncertainties and other factors

that may cause the actual results, level of activity, performance or achievements of Denison to be materially

different from those expressed or implied by such forward- looking statements. Denison believes that the

expectations reflected in this forward -looking information are reasonable but no assurance can be given

that these expectations will prove to be accurate and results may differ materially from those anticipated in

this forward-looking information. For a discussion in respect of risks and other factors that could influence

forward looking events, please refer to the factors discussed in Denison’s Annual Information Form dated

March 28, 2025 or subsequent quarterly financial reports under the heading ‘Risk Factors’. These factors

are not, and should not be construed as being, exhaustive.

Accordingly, readers should not place undue reliance on forward-looking statements. The forward-looking

information contained in this news release is expressly qualified by this cautionary statement. Any forward-

looking information and the assumptions made with respect thereto speaks only as of the date of this news

release. Denison does not undertake any obligation to publicly update or revise any forward- looking

information after the date of this news release to conform such information to actual results or to changes

in Denison's expectations except as otherwise required by applicable legislation.