Lolo Pass, elevation 5,233 feet (1,595 m), is a mountain pass in the western United States, in the Bitterroot Range of the northern Rocky Mountains. It is on the border between the states of Montana and Idaho, approximately forty miles (65 km) west-southwest of Missoula, Montana.

The Bitterroot Range is a mountain range and a subrange of the Rocky Mountains that runs along the border of Montana and Idaho in the northwestern United States. The range spans an area of 24,223 square miles (62,740 km2) and is named after the bitterroot, a small pink flower that is the state flower of Montana.