Achaeus was, according to nearly all traditions, a son of Xuthus and Creusa, and consequently a brother of Ion and grandson of Hellen. The Achaeans regarded him as the author of their race, and derived from him their own name as well as that of Achaia, which was formerly called Aegialus. When his uncle Aeolus in Thessaly, whence he himself had come to Peloponnesus, died, he went there and made himself master of Phthiotis, which now also received from him the name of Achaia. Servius alone calls Achaeus a son of Jupiter (Zeus) and Pithia, which is probably miswritten for Phthia, compare the account of Clement.