Cedar Lake is a 1,750-acre (7.0 km²) reservoir in southern Illinois, created by the damming of Cedar Creek, a tributary of the Big Muddy River, in 1974. The lake is located in Jackson County, southwest of Carbondale, Illinois. The lake is accessible from U.S. Highway 51. The lake was constructed for the purpose of supplying tap water to the residents of Carbondale. In addition, the lake serves fishing, swimming, and active recreation purposes.