Blueprint

DENISON MINESCORP.

/s/ Amanda Willett

Date: July 21, 2025

AmandaWillett

VicePresident Legal and Corporate Secretary

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Date: July 21, 2025

Commission File Number: 001-33414

Denison Mines Corp.

(Name ofregistrant)

1100-40 University Avenue

Toronto Ontario

M5J 1T1 Canada

(Address ofprincipal executive offices)

Indicate by check mark whether the registrant filesor will file annual reports under cover Form 20-F or Form40-F.

Form20-F ☐ Form 40-F ☒

Indicate by check mark if the registrant is submitting theForm 6-K in paper as permitted by Regulation S-T Rule101(b)(1): ☐

Indicate by check mark if the registrant is submitting theForm 6-K in paper as permitted by Regulation S-T Rule101(b)(7): ☐

SIGNATURES

Pursuant to the requirements of the Securities Exchange Actof 1934, the registrant has duly caused this report to be signed onits behalf by the undersigned, thereunto dulyauthorized.

FORM 6-KEXHIBIT INDEX

Exhibit Number		Description

99.1		Press release dated July 21,2025

pr-20250721mccleanlakesou

Exhibit 99.1

Denison MinesCorp.

1100– 40 University Ave

Toronto, ONM5J 1T1

www.denisonmines.com

PRESSRELEASE

Denison Announces Additional High-Grade

Uranium Mineralization Discovered at McClean South

Toronto, On – July 21, 2025. DenisonMines Corp. (“Denison” or the“Company”) (DML:TSX, DNN: NYSE American) is pleased toannounce that several significant new intercepts of shallowhigh-grade uranium mineralization have been discovered at theMcClean South zone (“McClean South”), which is part ofthe Company’s 22.5%-owned McClean Lake Joint Venture(“McClean Lake” or “MLJV”) in northernSaskatchewan (see Figure 1).

OranoCanada Inc. (“Orano Canada”), the 77.5% owner andoperator of the MLJV, completed a 6,400-metre exploration drillingprogram at McClean South during the first half of 2025. The drillprogram was highlighted by multiple notable high-gradeintersections at the 8C mineralized pod:

●

MCS-77 intersected 7.51% eU3O8over 5.4metres from 165.7 to 171.1metres (including 10.88% eU3O8over 3.7 metres),

●

MCS-80 intersected 3.5% eU3O8over 11.2metres from 156.7 to 167.9metres (including 5.81% eU3O8over 6.5 metres),and

●

MCS-84 intersected 1.72% eU3O8over 20.6metres from 150.6 to 170.7metres (including 4.43% eU3O8over 4.0 metres)

Intotal, fourteen of twenty-four completed drill holes from theprogram encountered significant intercepts of uraniummineralization and the results are interpreted to have confirmedand expanded the mineralized footprint of the 8C and 8W pods (seeFigure 2 and 3).

McCleanSouth is located approximately 600 metres to the south of theMcClean North deposit, where the MLJV recently commenced commercialmining using the joint venture’s patented SABRE miningmethod.

Chad Sorba, P.Geo., Denison’s Vice Presidentof Technical Services and Project Evaluation, commented“Earlierthis year, in its effort to follow up on the discovery of the 8Cpod at McClean South since the last drill program in 2022, OranoCanada carried out a successful exploration program that returnedseveral meaningful additional high-grade intercepts, which areinterpreted to have expanded the mineralized footprint of the 8Cand 8W pods.”

David Cates, Denison’s President & CEO,added “Wecongratulate and thank Orano Canada for its efforts to successfullyadvance the delineation and expansion of the high-grademineralization at McClean South. With the nearby McClean Northdeposit recently entering production using the jointventure’s SABRE mining method and Denison having madesignificant advancements in the de-risking of the In-Situ Recovery(‘ISR’) mining method in recent years, there is greatpotential for the MLJV to advance McClean South to potentiallyemerge as an economic new source of future feed to the McClean Lakemill.”

2025 McClean South Exploration Highlights

Theobjective of the exploration program at McClean South was to expandthe existing footprint of high-grade mineralization with a focus onfurther assessing the 8C and 8W Pods.

With uranium mineralization measuring greater than0.05% eU (0.06% eU3O8)intersected in 14 of 24 drill holes completed during the program,the results successfully expanded the footprint of the 8W and 8Cpods and confirmed the continuity ofmineralization.

Resultsfrom the 8W pod were highlighted by the following:

●

MCS-61 and MCS-64confirmed mineralization in thesandstone near surfacealong the western edge of the 8W pod.MCS-61 intersected 0.15% eU3O8over 2.2 metres from 40.3 to 42.5metres and MCS-64 intersected 0.21% eU3O8over 1.2 metres from 57.6 to 58.8metres.

Theresults of the holes discussed above and the balance of themineralized intersections from the 2025 drill program aresummarized in Table 1 below.

Table 1 – 2025 McClean Lake Exploration Drilling –Mineralized Intersections

Drill Hole	Target area	Orientation (azi/dip)	From (m)	To (m)	Length (m)(1)	% eU3O8(2)
MCS-61	8W	345°/-75°	40.3	42.5	2.2	0.15
MCS-62	8C	345°/-77°	173.9	176.9	3.0	0.52
including	-	-	175.6	176.0	0.4	1.71
MCS-63	8W	330°/-75°	174.3	175.6	1.3	0.31
MCS-64	8W	330°/-75°	57.6	58.8	1.2	0.21
MCS-67A	8C	340°/-70°	172.0	174.9	2.9	0.28
MCS-67A	-	-	175.9	183.2	7.3	0.29
MCS-67A	-	-	183.7	187.3	3.6	0.62
including	-	-	185.6	186.8	1.2	1.58
MCS-71	8C	348°/-80°	168.5	169.7	1.2	0.18
MCS-74	8C	345°/-80°	153.8	156.3	2.5	0.14
MCS-74	8C	-	157.2	164.7	7.5	0.24
MCS-74	8C	-	165.7	168.5	2.8	0.31
MCS-76	8C	349°/-80°	173.8	175.2	1.4	0.15
MCS-77	8C	345°/-80°	165.7	171.1	5.4	7.51
including	-	-	166.5	170.2	3.7	10.88
MCS-78	8C	345°/-83°	164.4	166.4	2.0	0.41
including	-	-	165.5	166.0	0.5	1.08
MCS-79	8C	345°/-78°	164.2	170.1	5.9	0.75
including	-	-	167.2	168.8	1.6	1.51
MCS-80	8C	346°/-80°	156.7	167.9	11.2	3.50
including	-	-	158.6	165.1	6.5	5.81
MCS-81	8C	345°/-77°	168.2	169.8	1.6	0.32
MCS-84	8C	345°/-90°	150.1	170.7	20.6	1.72
including	-	-	153.9	157.9	4.0	2.70
including	-	-	166.0	170.0	4.0	4.43

Notes:

(1) Lengthsindicated represent the down-hole length of mineralizedintersections;

(2) Interval iscomposited above a cut-off grade of 0.05% eU, which corresponds to0.06% eU3O8

Radiometric Equivalent Grades, Sampling, Analysis and DataVerification

Following the completion of a drill hole, the holeis radiometrically logged using a downhole slimline gamma probe,which collects continuous readings of radioactivity along thelength of the drill hole. Probe results are then calibrated usingan algorithm calculated from the comparison of probe resultsagainst geochemical analyses in the area. The gamma-log resultsprovide an immediate radiometric equivalent uranium value (eU%,then converted to eU3O8%)for the hole, which, except in very high-grade zones, is reasonablyaccurate. The Company typically reports eU3O8,as a preliminary result and subsequently reports definitive assaygrades following sampling and chemical analysis of the mineralizeddrill core. Assay sample intervals are generally 50 centimetreslong, except where higher or lower grade mineralization boundariesfall within the interval. In that case, two 25-centimetre samplesare collected. Flank samples of 1.0 metre are collected wheremineralization is located. Systematic geochemistry samples arecollected every 10 metres down the hole. All assayed core is splitin half, with one half retained and the other sent to the SRCGeoanalytical Laboratory in Saskatoon for analysis. Control samplesare routinely assayed with each batch of core samplesanalyzed.

About McClean South 8C, 8E and 8W Pods

The McClean South trend is located parallel to and approximately600 metres south of the McClean North trend in the southwesternportion of the property (see Figure 1). The McClean South zone hasbeen the subject of historic exploration drilling, resulting in thediscovery and subsequent delineation of the 8W, 8C, and 8E pods,which are situated along a N70° to 80° trend near theMcClean Lake granitic dome to the south (see Figure 2 and3).

Mineralization within the 8W, 8C and 8E pods is currentlyunderstood to be primarily hosted within the sandstone; however, ithas been locally encountered within the basement of the 8W and 8Cpods. The mineralization within the sandstone can extend upwards of50 meters above the unconformity and has been identified nearsurface at the western edge of the 8W pod.

No current resource estimate, prepared in accordance with NI43-101, exists for the mineralization identified to date at theMcClean South pods.

About McClean Lake

The McClean Lake property is located on the eastern edge of theAthabasca Basin in northern Saskatchewan, approximately 750kilometres north of Saskatoon. Denison holds a 22.5% ownershipinterest in the MLJV and the McClean Lake uranium mill, one of theworld’s largest uranium processing facilities. The mill haslicensed annual production capacity of 24.0 million poundsU3O8 and is currentlyoperating under a 10-year license expiring in 2027. The mill iscontracted to process the ore from the Cigar Lake mine under a tollmilling agreement (up to 18.0 million pounds U3O8 per year). TheMLJV is an unincorporated contractual arrangement between OranoCanada with a 77.5% interest and Denison with a 22.5% interest.Orano Canada is the operator of the project.

McClean Lake consists of nine known uranium deposits: JEB; Sue A,B, C, D, E and F; McClean North; and McClean South. In 1995, thedevelopment of the McClean Lake project began. Mill constructioncommenced in 1995, and ore processing activities reached commercialproduction in November 1999. Mining operations commenced in 1996,and the following deposits have been mined out to date: JEB (1996to 1997), Sue C (1997 to 2002), Sue A (2005 to 2006), Sue E (2005to 2008) and Sue B (2007 to 2008). Production from the McCleanNorth deposit, using the MLJV’s patented SABRE mining method,commenced in 2025.

About Denison

Denison is a leading uranium mining, development, and explorationcompany with interests focused in the Athabasca Basin region ofnorthern Saskatchewan, Canada. Denison has an effective 95%interest in its flagship Wheeler River Uranium Project, which isthe largest undeveloped uranium project in the infrastructure richeastern portion of the Athabasca Basin region of northernSaskatchewan. In mid-2023, the Phoenix feasibility study wascompleted for the Phoenix deposit as an ISR mining operation, andan update to the previously prepared 2018 Pre-Feasibility Study('PFS') was completed for Wheeler River's Gryphon deposit as aconventional underground mining operation. Based on the respectivestudies, both deposits have the potential to be competitive withthe lowest cost uranium mining operations in the world. Permittingefforts for the planned Phoenix ISR operation commenced in 2019 andseveral notable milestones were achieved in 2024 with thesubmission of federal licensing documents and the acceptance of thefinal form of the project's Environmental Impact Statement by theProvince of Saskatchewan and the Canadian Nuclear SafetyCommission.

Denison's interests in Saskatchewan also include a 22.5% ownershipinterest in the MLJV, which includes unmined uranium deposits (withmining at the McClean North deposit via the MLJV's SABRE miningmethod having commenced in 2025) and the McClean Lake uranium mill(currently utilizing a portion of its licensed capacity to processthe ore from the Cigar Lake mine under a toll milling agreement),plus a 25.17% interest in the Midwest Joint Venture Midwest Mainand Midwest A deposits, and a 70.55% interest in the Tthe HeldethTúé ('THT') and Huskie deposits on the Waterbury LakeProperty. The Midwest Main, Midwest A, THT and Huskie deposits arelocated within 20 kilometres of the McClean Lake mill. Takentogether, Denison has direct ownership interests in propertiescovering ~384,000 hectares in the Athabasca Basinregion.

Additionally, through its 50% ownership of JCU (Canada) ExplorationCompany, Limited ('JCU'), Denison holds interests in variousuranium project joint ventures in Canada, including the Millenniumproject (JCU, 30.099%), the Kiggavik project (JCU, 33.8118) andChristie Lake (JCU, 34.4508%).

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

For more information, please contact

DavidCates (416) 979-1991 ext. 362

President andChief Executive Officer

GeoffSmith (416) 979-1991 ext. 358

Vice PresidentCorporate Development & Commercial

Follow Denison onX (formerly Twitter) @DenisonMinesCo

Qualified Persons

The technical information contained in this press release has beenreviewed and approved by Chad Sorba, P.Geo., Denison’s VicePresident Technical Services & Project Evaluation, who is aQualified Person in accordance with the requirements of NI43-101.

Cautionary Statement Regarding Forward-LookingStatements

Certain information contained in this news release constitutes‘forward-looking information’, within the meaning ofthe applicable United States and Canadian legislation, concerningthe business, operations and financial performance and condition ofDenison. Generally, these forward-looking statements can beidentified by the use of forward-looking terminology such as‘plans’, ‘expects’, ‘budget’,‘scheduled’, ‘estimates’,‘forecasts’, ‘intends’,‘anticipates’, or ‘believes’, or thenegatives and/or variations of such words and phrases, or statethat certain actions, events or results ‘may’,‘could’, ‘would’, ‘might’ or‘will be taken’, ‘occur’, ‘beachieved’ or ‘has the potential to’.

In particular, this news release contains forward-lookinginformation pertaining to the following: the interpretation ofexploration results and expectations with respect thereto,including the interpretation of the results from the McClean LakeJV exploration program undertaken by Orano Canada, underlyingassumptions and the McClean Lake JV’s intentions with respectthereto; exploration plans and objectives; plans and objectives forISR and SABRE mining by Denison and/or Orano Canada; andexpectations regarding its joint venture ownership interests andthe continuity of its agreements with its partners and thirdparties. Statements relating to 'mineral reserves' or 'mineralresources' are deemed to be forward-looking information, as theyinvolve the implied assessment, based on certain estimates andassumptions that the mineral reserves and mineral resourcesdescribed can be profitably produced in the future.

Forward-looking statements are based on the opinions and estimatesof management as of the date such statements are made, and they aresubject to known and unknown risks, uncertainties and other factorsthat may cause the actual results, level of activity, performanceor achievements of Denison to be materially different from thoseexpressed or implied by such forward-looking statements. Forexample, the modelling and assumptions upon which theinterpretation of results are based may not be maintained afterfurther testing or be representative of actual conditions. Denisonbelieves that the expectations reflected in this forward-lookinginformation are reasonable but no assurance can be given that theseexpectations will prove to be accurate and results may differmaterially from those anticipated in this forward-lookinginformation. For a discussion in respect of risks and other factorsthat could influence forward-looking events, please refer to thefactors discussed in Denison’s Annual Information Form datedMarch 28, 2025 or subsequent quarterly financial reports under theheading ‘Risk Factors’. These factors are not, andshould not be construed as being exhaustive.

Accordingly, readers should not place undue reliance onforward-looking statements. The forward-looking informationcontained in this news release is expressly qualified by thiscautionary statement. Any forward-looking information and theassumptions made with respect thereto speaks only as of the date ofthis news release. Denison does not undertake any obligation topublicly update or revise any forward-looking information after thedate of this news release to conform such information to actualresults or to changes in Denison's expectations except as otherwiserequired by applicable legislation.

Figure 1 – McClean Lake Project Claims

Figure 2 – McClean Lake South 8C and 8E Pod – 2025Drilling

Figure 3 – McClean Lake South 8W Pod – 2025Drilling