The Warner sucker (Catostomus warnerensis) is a rare species of freshwater ray-finned fish in the family Catostomidae. Native to Oregon in the United States and found only in the Warner Basin, its distribution extends just into Nevada and California. It is a federally listed threatened species. Its other common name is redhorse. The International Union for Conservation of Nature has rated this fish as an endangered species because of its small extent of occurrence, the small number of locations in which it is found, and the extreme fluctuations in area of occupancy resulting from drought and water abstraction. Conservation efforts have been put in place.