Lost River Peak, also known as Lost River Mountain, is a 12,078-foot summit in Idaho’s Lost River Range within Salmon-Challis National Forest. It ranks as the sixth-highest peak in Idaho and the fifth-highest in its range. Located 1.8 miles southeast of Mount Breitenbach, its line parent, the mountain is one of the notable high points of central Idaho because of both its elevation and its standing among the state’s highest summits.