The
Tongue River (
Assiniboine:
Tacéži wakpá ) is a tributary of the
Yellowstone River, approximately 265 mi (426 km) long, in the
U.S. states of
Wyoming and
Montana. The Tongue rises in Wyoming in the
Big Horn Mountains, flows through northern Wyoming and southeastern Montana and empties into the Yellowstone River at
Miles City, Montana. Most of the course of the river is through the beautiful and varied landscapes of
eastern Montana, including the Tongue River Canyon, the Tongue River breaks, the pine hills of southern Montana, and the buttes and grasslands that were formerly the home of vast migratory herds of
American bison. The Tongue River watershed encompasses parts of the
Cheyenne and
Crow Reservations. The Headwaters lie on the Big Horn National Forest, and the watershed encompasses the Ashland Ranger District of the Custer National Forest.