Castle Crags Wilderness, Nature reserve in Shasta County, United States.

Castle Crags Wilderness is a 12,232-acre protected area in the Trinity Mountains of the Shasta-Trinity National Forest. Its southeastern section holds the Castle Crags, granite spires and domes resembling Yosemite's rock, while the north has glacial cirques and a wetter, east-trending divide. Elevations run from 2,500 to 7,300 feet.

The area was designated as a protected wilderness by Congress through the California Wilderness Act in 1984. The site was also the location of a conflict in 1855 that is now recognized as a California Historical Landmark.

The Wintu called the crags the Abode of the Devil, and Spanish explorers rendered it Castle del Diablo, Castle of the Devil. The name survives in the landscape rather than in any building: the spires themselves are the monument. Mineral springs at the base of the crags drew fur traders, and after the Southern Pacific Railroad arrived, health resorts opened nearby.

The area is accessible through multiple trailheads that connect to the Pacific Crest Trail and pass through conifer forests and rocky terrain. Most routes are challenging and require good physical fitness and preparation for changing weather conditions.

The 1855 Battle of Castle Crags, part of the Modoc War, was fought on a ridge saddle between Castle Lake and Battle Rock; the site is California Historical Landmark No. 16. Castle Lake itself, in a roadless area of about 7 km², sits in the largest glacial cirque of the wilderness.