SCHEDULE 13D 0001698535 XXXXXXXX LIVE Common Shares, no par value 06/24/2025 false 0001997377 46500E867 IsoEnergy Ltd.

217 Queen Street West, Suite 401 Toronto A6 M5V 0R2

Attn: Benjamin Salter (604) 428-4112 NexGen Energy Ltd. 1021 West Hastings Street, Suite 3150 Vancouver A1 V6E 0C3 0001698535 NexGen Energy Ltd. WC A1 16478746 0 16478746 0 16478746 N 30.9 CO Prior to the date the Issuer became a reporting issuer, the Reporting Person held 15,278,746 shares (31.8%). The Issuer became a reporting issuer on April 25, 2025. On June 24, 2025, the Reporting Person acquired an additional 1,200,000 common shares, in the ordinary course of business, as part of a larger equity offering of 5,121,500 common shares by the Issuer. Common Shares, no par value IsoEnergy Ltd. 217 Queen Street West, Suite 401 Toronto A6 M5V 0R2 NexGen Energy Ltd. 1021 West Hastings Street Vancouver, British Columbia V6E 0C3 Canada Mining No No British Columbia, Canada Working capital Reporting Person previously held 15,278,746 common shares of the Issuer, approximately 31.8% of the Issuer's outstanding shares prior to the date the Issuer became a U.S. reporting Issuer. On June 24, 2025, the Reporting Person purchased an additional 1,200,000 common shares of the Issuer, in the ordinary course of business, at a price of C$10.00 per share, in connection with a larger equity offering of 5,121,500 common shares by the Issuer (which increased the Issuer's total outstanding shares to 53,267,314 common shares). 30.9% 16,478,746 Issuer private placement offering N/A N/A None None NexGen Energy Ltd. /s/ Benjamin Salter 06/25/2025