Fontenelle Reservoir is an artificial reservoir located in southwest Wyoming. It lies almost entirely within Lincoln County, although the east end of the Fontenelle Dam and a tiny portion of the reservoir are actually in northwestern Sweetwater County. Impounded by Fontenelle Dam, the reservoir acts primarily as a storage reservoir for the U.S. Bureau of Reclamation's Colorado River Storage Project, retaining Wyoming water in the state as a means of asserting Wyoming's water rights, with a secondary purpose of power generation. Water from Fontenelle Reservoir is used in local industries such as mining and power generation. Although initially projected to provide irrigation water for agriculture, the irrigation component was downgraded after difficulties with efficient irrigation in Wyoming's high semi-desert became apparent.
Plagued by chronic leakage problems at the dam, the reservoir was hurriedly emptied in 1965 and 1986 amid concerns about dam failure. The reservoir has facilities for recreation, with boat launching ramps and campgrounds. Fishing is available for brown, cutthroat and rainbow trout.