segment of the northern Rocky Mountains in the United States, extending east-southeastward for 50 miles (80 km) from the Stillwater River, in southern Montana, to the Clarks Fork of the Yellowstone River, in northwestern Wyoming. Many peaks rise to more than 12,000 feet (3,700 m), including Granite Peak (12,799 feet 【3,901 m】), the highest point in Montana. It was through these mountains that Chief Joseph led the Nez Percé Indians on their attempt to reach Canada in 1877.

The range serves as a source region for the Clarks Fork (stream) and includes the Granite Range (a northwestern extension), parts of the Gallatin, Custer, and Shoshone national forests, and the Absaroka Beartooth Wilderness area. Scenic granite formations, alpine peaks, high plateaus, glaciers, and lakes attract many tourists.