The Big Sandy River flows through southwest Wyoming in Sublette and Sweetwater counties, serving as a tributary to the Green River drainage system. This 52-mile stretch of river upstream of Big Sandy Reservoir has been the focus of one of Wyoming's most significant native fish restoration projects. The river originates in the Wind River Range and flows northeast through sagebrush steppe terrain before feeding into Big Sandy Reservoir. Following major conservation efforts that included rotenone treatments between 2021-2024, the river has been transformed from a system dominated by non-native species to one that now supports healthy populations of native fish alongside improved sport fishing opportunities.