Denison Reports Assays Increase Grades by 45% and Deliver Most Meaningful Gryphon D-Lens Result to Date at Wheeler River

Denison Mines Corp.

TORONTO, ONTARIO--(Marketwired - May 26, 2017) - Denison Mines Corp. ("Denison" or the "Company") (TSX:DML)(NYSE MKT:DNN) is pleased to report a significant increase in uranium grades from previously released preliminary radiometric probe results, following the receipt of uranium assays from the Company's winter 2017 drilling program on the 60% owned Wheeler River project. The winter 2017 exploration program involved a combination of infill drilling at the Gryphon deposit and resource expansion exploration drilling to the northwest of the Gryphon deposit. The Wheeler River project is host to the high-grade Gryphon and Phoenix uranium deposits, and is the largest undeveloped high-grade uranium project in the infrastructure rich eastern portion of the Athabasca Basin region in northern Saskatchewan.