Boysen Reservoir is a reservoir formed by Boysen Dam, an earth-fill dam on the Wind River in the central part of the U.S. state of Wyoming. It is near the town of Shoshoni in Fremont County. The dam was constructed between 1947 and 1952 at the mouth of Wind River Canyon, just upstream from a previous dam that had been built by Asmus Boysen in 1908 on land he had leased from the Shoshone and Arapaho tribes. The dam and much of the reservoir are physically located on the Wind River Indian Reservation.

Surrounding the reservoir is Boysen State Park, run by the state of Wyoming. It includes 11 campgrounds spread around the reservoir and nearby area. The reservoir is a popular sporting area with numerous species of fish including walleye, perch, crappie and several species of trout.