South Holston Dam is a hydroelectric and flood control dam on the South Fork Holston River in Sullivan County, in the U.S. state of Tennessee. It is the uppermost of three dams on the South Fork Holston owned and operated by the Tennessee Valley Authority, which built the dam in the 1940s as part of efforts to control flooding in the Tennessee River watershed. On October 21, 1950 the valve gate closed and water began backing up to create South Holston Reservoir.