Denison Mines Corp.  provided a progress update on the In-Situ Recovery ("ISR") field test activities occurring at Phase 1 of the high-grade Phoenix uranium deposit ("Phoenix") at the Company's 90% owned Wheeler River Uranium Project ("Wheeler River" or the "Project"). The Company is also pleased to announce the discovery of additional high-grade uranium mineralization, including 22.0% eU3O8 over 8.6 metres in drill hole GWR-045, located outside of the existing high-grade resource domain associated with Zone A and Phase 1 of the phased mining approach currently planned for Phoenix. Interim progress highlights from the 2021 ISR field program include the following: Completed installation of commercial-scale wells: All five new commercial-scale well ("CSW") installations planned for the Test Pattern, located in the Phase 1 area of Phoenix, are complete. The Test Pattern consists of the newly installed five-spot pattern (GWR-038 to GWR-042), and GWR-032, which was installed in 2019. Taken together, the CSWs are spaced between 5 and 30 metres apart and are expected to facilitate further hydrogeologic testing and assessment of down-hole permeability enhancement tools as part of the ongoing field program. Successful installation of monitoring wells: Nine of eleven monitoring wells ("MWs") have been successfully installed within the Phase 1 area and outfitted with the associated materials and monitoring equipment to facilitate ongoing observation of the current and future hydrogeological test work – allowing for detailed hydrogeological assessment and water quality sampling. The final two MWs are expected to be completed in early August. Collected baseline hydrogeologic information and deployed permeability enhancement: The MaxPERF drilling tool was successfully deployed in all planned CSWs to create a series of lateral drill holes (penetration tunnels) designed to mechanically engineer increased access to the existing permeability of the ore zone formation. Discovery of High-Grade Mineralization in GWR-045: GWR-045 was completed as part of the ISR field test program to install MWs to the northwest of the five-spot Test Pattern. Based on the Phoenix block model, GWR-045 was expected to intersect low-grade uranium mineralization along the northwestern margin of the deposit, approximately 5 metres outside of the boundary of the Phoenix Zone A high-grade resource domain. The drill hole, however, intersected a thick interval of high-grade unconformity-associated uranium mineralization grading 22.0% eU3O8 over 8.6 metres. The high-grade mineralization intersected by GWR-045 remains open to the northwest, representing an area for further exploration and potential mineral resource expansion of Phoenix. Denison's exploration team is currently incorporating the results of GWR-045 into the Phoenix geological model to evaluate the potential to extend the high-grade domain with additional exploration drilling in the Phase 1 area of Phoenix. Once the final two MWs are completed, the Test Pattern will be ready for additional hydrogeologic test work, including the following planned activities:  Multi-day pump and injection tests to be conducted on the full-scale Test Pattern. These tests are intended to assess the Test Pattern's total permeability, and support an ongoing assessment of the ability of various permeability enhancement tools to normalize the varying levels of permeability associated with the natural fracture/structure network of the deposit; Ion tracer tests will be conducted by injecting and recovering solution with dissolved inorganic salts throughout the full-scale Test Pattern. This process is expected to (1) establish breakthrough times for each CSW, with injection from the centre well in the Test Pattern and recovery from the outer ring wells, and (2) confirm modelling of sub-surface pathways. Taken together, this test is expected to provide a more complete understanding of the hydrogeologic characteristics expected throughout Phase 1 and the necessary datasets for the design and permitting of a lixiviant test planned to make use of the same Test Pattern in 2022; Deployment and evaluation of additional permeability enhancement techniques based on individual well characteristics and associated hydrogeological assessments; and Extensive collection and analysis of permeameter samples from new and historic drill core for the assessment of matrix permeability spatially distributed throughout the areas representative of all of the mining phases planned for Phoenix.