The Tongue River is a tributary of the Yellowstone, approximately 265 mi (426 km) long, in the U.S. states of Wyoming and Montana.

It rises along the northern slope of the Bighorn Mountains in north central Wyoming and flows northeast, past the town of Sheridan, and then into Montana, forming the eastern boundary of the Northern Cheyenne Indian Reservation. It joins the Yellowstone near the town of Miles City.

On August 4, 1873, the river was the site of an early engagement between the U.S. Cavalry under George Armstrong Custer and the Sioux, prior to the Battle of the Little Bighorn.

See also

• List of Wyoming rivers
• List of Montana rivers