| Black Sandy State Park | |
| Map: | USA Montana |
| Relief: | 1 |
| Location: | Lewis and Clark County, Montana, United States |
| Nearest City: | Helena, Montana |
| Coordinates: | 46.7569°N -111.8897°W |
| Area Acre: | 43 |
| Elevation: | 3904feet |
| Designation: | Montana state park |
| Established: | 1980 |
| Visitation Num: | 43,966 |
| Visitation Year: | 2023 |
| Visitation Ref: | [1] |
| Administrator: | Montana Fish, Wildlife & Parks |
| Website: | Black Sandy State Park |
Black Sandy State Park is a public recreation area on the western shore of Hauser Lake reservoir, an impoundment of the Missouri River, located 13miles northeast of Helena in Lewis and Clark County, Montana, in the United States. The park is along the Lewis and Clark National Historic Trail.
Prior to 1980, Montana Power Company owned the land and operated the park as a recreation area. In 1980, the company turned over management of the park to the Montana Department of Fish, Wildlife and Parks (FWP). In 1982, it was designated a state recreation area. Subsequently, the land was also turned over to FWP.
Recreational activities available at the park include hiking, tent and RV camping, swimming, picnicking, fishing, boating, and water skiing. Fish species include rainbow and brown trout, walleye, and perch.
In 2012, a prefabricated concrete office building was proposed to replace a wooden 8feetx12feetft (xft) building with a 16feetx24feetft (xft) concrete building with internet access at a cost of $40,000.
Just south of the park, the White Sandy Recreation Area operated by the United States Bureau of Land Management has campsites and other amenities.