The Moab uranium mill tailings pile is a uranium mill waste pond situated alongside the Colorado River, currently under the control of the U.S. Department of Energy. Locals refer to it as the Moab Tailings Pile. In 1952 U.S. geologist Charles Steen found the largest uranium deposit in the United States near Moab, Utah. The uranium was processed by the Uranium Reduction Company and the waste slurry was stored in an unlined pond adjacent to the river. The Uranium Reduction Company was sold in 1962 and renamed the Atlas Uranium Mill.

After the mill was closed in 1984 the pond was capped. There was also a pile of mine tailings that was over 90 ft (27 m) tall at its highest point. It is believed that pollutants from the waste tailings are leaching into the river, inferred from the lethal effect on fish, primarily from high concentrations of ammonia. The site was transferred to the United States Department of Energy for remediation under Title 1 of the Uranium Mill Tailings Radiation Control Act in 2001. In August 2005 the Department of Energy announced that 11.9 million short tons (10.8 million tonnes) of radioactive tailings would be moved, mostly by rail, and buried in a lined hole. The proposed holding site is public land at Crescent Junction, Utah, about 30 mi (48 km) from the Colorado River. In February 2006 a final Environmental Impact Statement met with United States Environmental Protection Agency approval. The cost of the relocation was originally estimated to be $300 million, but 2008 Department of Energy estimates are in excess of $720 million.

The contract for the first transfer of the tailings has been awarded and the first relocation is expected to occur in late 2008. A series of works to extract and evaporate the water and ammonia from the pile before it reaches the Colorado River has been completed.

The tailings pile left untouched until the late 2010s. Trace amounts of uranium contamination were found in the Colorado River. The tailings were at risk of contaminating the Californian water supply and cleanup promptly began. However, the tailings were not fully removed before trace amounts of uranium were spread across the Great Basin Desert.