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Denison Announces Agreements with Skyharbour Resources, Increasing Denison’s Strategic Foothold Surrounding Wheeler River

Property Options & Staking

Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

PRESS RELEASE

Denison Announces Agreements with Skyharbour Resources, Increasing

Denison’s Strategic Foothold Surrounding Wheeler River

Toronto, ON – November 17, 2025. Denison Mines Corp. (“Denison” or the “Company”) (TSX: DML;

NYSE American: DNN) is pleased to announce that it has executed an agreement (the “Agreement”) with

Skyharbour Resources Ltd. (“Skyharbour”) (TSX-V:SYH) (OTCQX: SYHBF), (Frankfurt:SC1P) to acquire

initial interests in claims comprising Skyharbour’s Russell Lake Uranium Project (“Russell”), which is

located directly adjacent to Denison’s flagship Wheeler River Project (“Wheeler River”).

The Russell property will be divided into four property joint ventures that will be known as: Russell Lake

(“RL” or “Russell Lake”), Getty East, Wheeler North, and Wheeler River Inliers, of which Denison will

acquire initial ownership interests of 20%, 30%, 49%, and 70%, respectively. In addition, Denison and

Skyharbour have agreed to enter into option agreements (the “Earn-In Option Agreements”), which will

allow Denison to increase its ownership interest in each of the new Wheeler North and Getty East joint

ventures to up to 70% (collectively with the acquisition of initial interests, the “Transaction”).

David Cates, President & CEO of Denison, commented, “As Denison nears receipt of final regulatory

approvals for the Phoenix In-Situ Recovery mine proposed for our flagship Wheeler River property,

we are also making measured investments in our project pipeline – including our next development

assets and high-potential exploration properties. Given its proximity to Wheeler River, Denison has

had an interest in adding Russell to our property portfolio for much of my nearly two decades with

the Company. This transaction achieves that objective by providing Denison with the opportunity

to lead and participate in exploration efforts across four newly created joint ventures, which are

designed to drive collaboration between Denison and Skyharbour’s technical teams. We are excited

to build on our long-standing relationship with Skyharbour and accelerate the evaluation of this

exceptional package of highly prospective ground.”

Jordan Trimble, President and CEO of Skyharbour, stated: “This is a transformative transaction for

Skyharbour and our shareholders as it represents a major stamp of approval for Russell. We are

very pleased to expand upon our long-standing relationship with Denison and to partner with their

team to advance one of the more prospective exploration projects in the Athabasca Basin proximal

to existing and developing mines. Denison’s success in exploring, permitting, and developing the

neighbouring world-class Wheeler River Project will provide considerable insight and experience

as we jointly pursue success at Russell. Further, this Transaction delivers on our belief that Russell

should be treated as multiple different projects due to the abundance of targets and sheer scale of

the land package in one of the most prolific uranium exploration corridors in the world. The

structure and terms of the Agreement allow Skyharbour to continue exploring as operator at the

majority of the claims at Russell while retaining upside in future success Denison may have at the

Wheeler North, Getty East and Wheeler River Inlier claims.”

Under the terms of the Agreement, Denison has agreed to pay Skyharbour total consideration of $18.0

million (“the Consideration Payment”) – consisting of a $2.0 million cash payment upon the execution of

the Agreement (“the Upfront Payment”) and deferred consideration of $16 million, payable in cash or

common shares of Denison in two tranches of $8.0 million (“the Deferred Consideration”), before

December 31, 2025. Closing of the Transaction (“Closing”) is expected to occur on or before December

21, 2025.

Key Transaction Highlights:

• Strengthens Denison’s regional presence and establishes a strategic foothold immediately east

and north of the Company’s flagship Wheeler River Property, with a high potential land package

that stands to benefit from its proximity to a property where the Phoenix and Gryphon deposits are

located.

• Supports Denison’s long-term growth objectives and exploration strategy by augmenting its vast

portfolio of exploration properties with key claims that will benefit from the joint exploration expertise

of Denison and Skyharbour.

• Promotes exploration activity and increases the likelihood of exploration success near the Wheeler

River Project, meaningfully enhancing Denison’s exposure to high potential and value-adding

discovery opportunities.

• Gives Denison a pathway to majority ownership through multi-phase earn-in options to increase its

ownership interests in Wheeler North and Getty East, allowing for disciplined capital deployment

tied to exploration results.

Formation of Exploration Joint Ventures

Upon closing of the Transaction, Russell will be subdivided into four joint ventures, (outlined in Figure 1),

consisting of Wheeler North, RL, Wheeler River Inliers, and Getty East.

• Wheeler North (49% DML, 51% SYH; subject to additional earn-in options)

Represented by the yellow claims in Figure 1, the Wheeler North claims are adjacent to the

Northeast boundary of Wheeler River. Comprised of 16,409 hectares over 8 claims. Upon closing

of the Transaction, Denison will have the option to increase its interest in Wheeler North to a 70%

interest in these claims and Denison will become the operator of Wheeler North as described in

more detail below.

• RL (20% DML, 80% SYH)

Represented by the pink claims in Figure 1, the Russell Lake claims are adjacent and to the east

of Wheeler River and comprise 53,192 hectares over 16 claims. In order to maintain its initial

interest in RL, Denison has agreed to fund its pro rata share of up to a maximum of C$10.0 million

in total project expenditures. Upon the closing of the Transaction, Skyharbour will remain operator

of RL.

• Wheeler River Inliers (70% DML, 30% SYH)

Represented by the blue claims in Figure 1, the Wheeler River Inliers comprise a total of 608

inlaying hectares within the boundaries of Wheeler River. Upon closing of the Transaction, Denison

will become operator of Wheeler River Inliers.

• Getty East (30% DML, 70% SYH; subject to additional earn-in options)

Represented by the green claim in Figure 1, the Getty East claim of 3,105 hectares is located fewer

than 10km southeast of Wheeler River, and borders Cameco’s Cree Zimmer property which holds

its Key Lake operations to the south. Upon the closing of the Transaction, Skyharbour will remain

operator of Getty East; however, Denison will have the option to become the operator and acquire

up to a 70% interest in this joint venture as described in more detail below.

Figure 1: Russell Lake Uranium Property - Claim Map

Key Terms of the Transaction:

Immediately upon execution of the Agreement an upfront payment of $2.0 million in cash will be payable to

Skyharbour, with a deferred consideration of $16.0 million payable prior to December 31, 2025. The

Deferred Consideration will be comprised of two tranches, each of which may be paid in cash or shares at

Denison’s election. This first deferred payment of $8.0 million in cash or shares, is payable on or before the

fifth business day prior to December 21, 2025. The second deferred payment of $8.0 million in cash or

shares, is payable within 10 days of December 21, 2025.

The Agreement grants Denison priority access to excess capacity at Skyharbour’s existing Russell

exploration camp located near Highway 914 proximal to McGowan Lake (the “Camp”), which Skyharbour

will continue to operate. Denison will pay Skyharbour a usage fee as well as a 7% administrative fee to use

the Camp.

The Transaction is subject to customary approvals, including Skyharbour obtaining TSX Venture exchange

approval. The Transaction will be considered a Reviewable Transaction under TSX Venture exchange

policies as David Cates, President, CEO & Director of Denison, is also a director of Skyharbour.

Key Terms of the Earn-In Option Agreements:

The Earn-In Option Agreements grant Denison an option to earn additional interests in Wheeler North and

Getty East.

Wheeler North Earn-In Option

Under the terms of the Wheeler North Earn-In Option Agreement, Denison may acquire up to a 70% interest

in Wheeler North. The option agreement contains two (2) phases, as summarized below:

Phase 1: To earn an additional 11% interest in Wheeler North (increasing Denison’s ownership to 60%),

Denison must:

• Incur $10.0 million in exploration expenditures at Wheeler North within 48 months of Closing,

of which $2.5 million in exploration expenditures must be completed within 24 months of

Closing, and

• Make a cash payment in the amount of $1.5 million to Skyharbour within 48 months of Closing.

Phase 2: To earn an additional 10% interest (increasing Denison’s ownership to 70%) in Wheeler North,

Denison must complete the requirements of Phase 1, plus the following:

• Incur an additional $15.0 million in exploration expenditures at Wheeler North within 7 years of

Closing, and

• Make a further cash payment in the amount of $2.0 million to Skyharbour within 7 years of

Closing.

Getty East Earn-In Option Agreement

Under the terms of the Getty East Option Agreement, Denison may acquire up to a 70% interest in Getty

East. The option agreement contains two (2) phases, as summarized below.

Phase 1: To earn an additional 19% interest in Getty East (increasing Denison’s ownership to 49%),

Denison must incur $5.0 million in exploration expenditures at Getty East within 48 months of Closing, of

which $1.5 million must be completed within the first 24 months of Closing.

Phase 2: To earn an additional 21% interest in Getty East (increasing Denison’s ownership to 70%),

Denison must complete the requirements of Phase 1, plus incur an additional $10 million in exploration

expenditures within 7 years of Closing. Upon completion of the Phase 2 earn-in option criteria, Denison

will have the option to become the operator in this joint venture.

About Denison

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% 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.

For more information, please contact

David Cates (416) 979-1991 ext. 362

President and Chief Executive Officer

Geoff Smith (416) 979-1991 ext. 358

Vice President Corporate Development & Commercial

Follow Denison on X (formerly Twitter) @DenisonMinesCo

About Skyharbour

Skyharbour holds an extensive portfolio of uranium exploration projects in Canada's Athabasca Basin and

is well positioned to benefit from improving uranium market fundamentals with interest in thirty-seven

projects covering over 616,000 hectares (over 1.5 million acres) of land. Skyharbour has acquired from

Denison Mines, a large strategic shareholder of the Company, a 100% interest in the Moore Uranium

Project, which is located 15 kilometres east of Denison's Wheeler River project and 39 kilometres south of

Cameco's McArthur River uranium mine. Moore is an advanced-stage uranium exploration property with

high-grade uranium mineralization in several zones at the Maverick Corridor. Adjacent to the Moore Project

is the Russell Lake Uranium Project, which hosts widespread uranium mineralization in drill intercepts over

a large property area with exploration upside potential. The Company is actively advancing these projects

through exploration and drilling programs.

Skyharbour also has joint ventures with industry leaders Denison Mines, Orano Canada Inc., Azincourt

Energy, and Thunderbird Resources at the Russell, Preston, East Preston, and Hook Lake Projects,

respectively. The Company also has several active earn-in option partners, including CSE-listed Basin

Uranium Corp. at the Mann Lake Uranium Project; TSX-V listed North Shore Uranium at the Falcon Project;

UraEx Resources at the South Dufferin and Bolt Projects; Hatchet Uranium at the Highway Project; CSE-

listed Mustang Energy at the 914W Project; and TSX-V listed Terra Clean Energy at the South Falcon East

Project.

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 Denison. 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 Agreement, Earn-In Option Agreements and ancillary agreements and the expected

benefits thereof; the assumption that the transactions set forth in the agreements with Skyharbour will be completed as described; the

Company’s exploration, development and expansion plans and objectives; 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 acti vity,

performance or achievements of Denison to be materially different from those expressed or implied by such forward -looking

statements. For example, the parties to the Option Agreement may not complete the option phases as described and/or the exploration

objective for the Exploration Properties may not be achieved. In addition, Denison may decide or otherwise be required to discontinue

testing, evaluation and other work on the Company’s other properties if it is unable to maintain or otherwise secure the necessary

resources (such as testing facilities, capital funding, joint venture approvals, regulatory approvals, etc.). 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 a nticipated 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 under the heading ‘Risk Factors’ or in subsequent quarterly financial reports. 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.