In Greek mythology, Xuthus was a son of Hellen and Orseis and founder (through his sons) of the Achaean and Ionian nations. He had two sons by Creusa: Ion and Achaeus and a daughter named Diomede. Aiclus and Cothus are sometimes described as being his children.

Euripides' play Ion provides an unusual alternate version, according to which Xuthus is son of Aeolus and Cyane and Ion has in fact been begotten on Xuthus' wife Creusa by Apollo. Xuthus will later father Dorus with Creusa, though Dorus is normally presented as Xuthus' brother.