Tongue River Reservoir State Park, Montana state park in Big Horn County, US.

Tongue River Reservoir State Park is a state park in Montana centered around a reservoir surrounded by red shale cliffs and juniper canyons. The park provides camping areas, boat access, and space for fishing and water activities throughout the year.

The sources do not record a founding date or the agency that established Tongue River Reservoir State Park; the reservoir itself is a 12-mile impoundment of the Tongue River, and the park occupies 642 acres on its western shore six miles north of Decker. Its fishing is managed for crappie, smallmouth bass, northern pike and walleye, with the reservoir regularly stocked.

The reservoir is managed for crappie, smallmouth bass, northern pike and walleye, and it is regularly stocked, so anglers plan trips around those four species. A seasonal marina serves boaters, and the 12-mile-long water draws fishermen from Montana and neighbouring Wyoming.

The park lies 6 miles north of Decker on the reservoir's western shore, at 3,468 feet. A seasonal marina and boat ramps give access to the 12-mile-long water; camping areas sit along the shore. The reservoir is regularly stocked, with crappie, smallmouth bass, northern pike and walleye as the management targets.

The reservoir is regularly stocked and managed for crappie, smallmouth bass, northern pike and walleye, so anglers know which four species to target. The water covers 3,600 acres within a 12-mile-long impoundment of the Tongue River.