Old Desolate is a multi-summit, ridge-like mountain located in Mount Rainier National Park, in Pierce County of Washington state. It is part of the Cascade Range, and lies due north of the summit of Mount Rainier. The Wonderland Trail provides an approach to this mountain, and the summit offers views of Sluiskin Mountain and Mount Rainier. Burroughs Mountain is its nearest higher neighbor, to the southeast. Precipitation runoff from Old Desolate drains east into the West Fork White River, or west into the Carbon River.