Big Sandy Dam is a dam in Sweetwater County, Wyoming, about ten miles north of Farson.
The earthen dam impounds the Big Sandy River and stands 85 feet high. It was built from 1941 to 1952 by the United States Bureau of Reclamation as part of its Eden Project for irrigation storage. No hydroelectric power is generated here. The dam is operated by the local Eden Valley Irrigation and Drainage District.
Big Sandy Reservoir has a surface area of about and contains a maximum capacity of . The lake allows for boating, camping and fishing recreation with primitive facilities.