Keyhole State Park is a state park located in Crook County in northeastern Wyoming, USA, near the town of Moorcroft. The park is known for its Sioux heritage, and its accommodation of outdoor sports.
The adjacent Keyhole Reservoir was formed by the Keyhole Dam project of the United States Bureau of Reclamation, completed in 1952. The reservoir has a total capacity of 334,200 acre-feet and water surface of 13,700 acres, which provides storage for irrigation, flood control, fish and wildlife conservation, recreation, sediment control, and municipal and industrial water supply.
Despite being located in Wyoming, the reservoir is owned by the state of South Dakota and is used to supply water to several western South Dakota communities.