South Fork Eel River Wilderness is a 12,868-acre protected area in Mendocino County, California, added to the National Wilderness Preservation System in 2006 and managed by the Bureau of Land Management. It includes the Red Mountain and Cahto Peak units. Red Mountain is notable for steep terrain, striking reddish ultrabasic and serpentine-derived soils, and a specialized plant community with rare and endangered species, including the northern range extension of Sargent cypress and the only known locations of Red Mountain buckwheat and Red Mountain stonecrop. The Cahto Peak Unit contains largely undisturbed Douglas fir watersheds, including Elder Creek, recognized for its exceptional ecological and scientific importance.