| Boysen State Park | |
| Photo Width: | 280 |
| Photo Alt: | Picnic area beneath mountains |
| Map: | Wyoming |
| Map Width: | 280 |
| Relief: | 1 |
| Label: | Boysen State Park |
| Location: | Fremont County, Wyoming, United States |
| Coords: | 43.3189°N -108.1839°W |
| Area: | 35952acres |
| Elevation: | 4728feet |
| Established: | 1956 |
| Free Label: | Named for |
| Free Data: | Asmus Boysen |
| Designation: | Wyoming state park |
| Administrator: | Wyoming State Parks, Historic Sites & Trails |
Boysen State Park is a public recreation area surrounding the Boysen Reservoir, an impoundment of the north-flowing Wind River, in Fremont County, Wyoming. The state park covers more than at the south end of the Owl Creek Mountains at the mouth of the Wind River Canyon.
The park was established in 1956 following completion of the Boysen Dam in 1951. It is named for Asmus Boysen, who built the site's first dam in 1908. Part of the original dam can still be seen.
According to the Köppen Climate Classification system, Boysen Dam has a cold semi-arid climate, abbreviated "BSk" on climate maps. The hottest temperature recorded at Boysen Dam was on July 4, 1954, while the coldest temperature recorded was on January 31, 1979.
The park offers multiple campgrounds, boat launches, and a privately operated marina. Game fish found in the reservoir include walleye, sauger, perch, crappie, ling, rainbow, cutthroat, and brown trout.