White Cap Peak is an 11,899-foot summit in Idaho’s Lost River Range of the Rocky Mountains, in Custer County within Salmon–Challis National Forest. It is the eighteenth-highest peak in Idaho and stands among several of the state’s loftiest mountains, near Leatherman Peak, Mount Morrison, and Borah Peak. Its topographic relief is dramatic, rising 5,600 feet above Highway 93 in the Big Lost River Valley over four miles and 1,800 feet above Pass Lake in less than half a mile. Runoff from its slopes drains both toward the Big Lost River and into the headwaters of the West Fork Pahsimeroi River. The peak has an alpine subarctic climate with severe winters and cool to warm summers.