The Tongue River is a tributary of the Yellowstone 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.

At the Battle of the Tongue River, Brigadier General Patrick Edward Connor routed an Indian force along the river on August 29, 1865. Then on August 4, 1873, the river was again the site of an engagement between the U.S. Cavalry under George Armstrong Custer and the Sioux, prior to the Battle of the Little Bighorn.


The impounded Tongue River provides a 12-mile long reservoir set in the scenic red shale and juniper canyons and open prairies of southeastern Montana. Large bodies of water such as this are rare in this prairie country and 50,000 visitors flock each year to enjoy the recreational opportunities.