Castle Mountain is a 12,617-foot peak in the Beartooth Mountains of southern Montana, about 15 miles east-northeast of Cooke City. Located in the Absaroka–Beartooth Wilderness within Gallatin and Custer National Forests, it stands just outside Yellowstone National Park’s northern boundary. It is the third-highest summit in the Beartooth Mountains and the highest point in Carbon County, Montana. Its importance lies in both its elevation and its setting amid some of the region’s most rugged protected high country, where designated wilderness and proximity to Yellowstone make it a notable landmark.