Rio Blanco is a stream that is tributary of the San Juan River in southern Colorado, United States. The stream originates in the San Juan Mountains and flows for through the San Juan National Forest and private lands to its confluence with the San Juan River in Archuleta County, Colorado. Colorado classifies the Rio Blanco as an Aquatic Life Coldwater Class 1/Recreation Class 1 waterway supporting water supply and agricultural uses. The river also features native cutthroat trout and introduced rainbow trout fishing.