Horse , common name for the domestic horse and three groups of undomesticated species. One group comprises the zebra, native to Africa; another consists of the , including the kiang and onager of Asia and the wild of Africa. The third group contains Przhevalski's horse, now extinct in the wild. The only extant true wild horse, it crosses with the domestic horse and produces fertile progeny. Other so-called wild horses in various parts of the world are descendants of domestic horses that have reverted to the wild state .