Echinomastus mariposensis (syn. Neolloydia mariposensis, Sclerocactus mariposensis) is a rare species of cactus known by the common names Lloyd's fishhook cactus, golfball cactus, silver column cactus, and Mariposa cactus. It is native to a small section of territory straddling the border between Brewster County, Texas, in the United States and the state of Coahuila in Mexico. It has been federally listed as a threatened species in the United States since 1979.