Big Sandy Dam (National Inventory of Dams ID WY01387) 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 2,500 acres (10 km) and contains a maximum capacity of 38,300 acre-feet (47 million cubic meters). The lake allows for boating, camping and fishing recreation with primitive facilities.