The Lost River sucker (Deltistes luxatus) is a species of ray-finned fish in the family Catostomidae. It is the only living member of the genus Deltistes. It is found only in California and Oregon. Its population is much reduced from historical numbers for a number of reasons. It is federally listed as an endangered species of the United States. This species is known as the C'waam by the local Native American Nation, the Klamath Tribes.