Pryor Mountains National Forest was a short-lived U.S. national forest in Montana's Pryor Mountains. Established as the Pryor Mountains Forest Reserve on November 6, 1906, with 78,732 acres, it became a national forest on March 4, 1907. Its independent existence lasted only a little more than a year before, on July 1, 1908, it was merged with part of Yellowstone National Forest to create Beartooth National Forest, ending the Pryor Mountains name as a separate forest. The land now forms the Pryor Mountains unit of the Beartooth Ranger District in Custer National Forest in Carbon County, Montana.