Lost Trail Pass is a mountain pass in the Rocky Mountains of the northwestern United States, on the border of Idaho and Montana in the Bitterroot Mountains. The pass is at an elevation of 7,014 feet above sea level and is traversed by U.S. Highway 93. The pass is about a half mile west of the Continental Divide, which retreats eastward at this point, inside Montana along the Ravalli–Beaverhead County border, toward Butte.