Acastus, in mythology, son of Pelias (see neleus); he took part in the Argonautic expedition and the Calydonian boar-hunt (see argonauts; meleager (1)). When Peleus took refuge with him, Acastus' wife (variously named) loved him, and being repulsed, accused him to her husband of improper advances. Acastus, therefore, stole Peleus' wonderful sword and left him alone on Mt. Pelion, where he was rescued by Chiron (see centaurs). Afterwards Peleus took Iolcus, putting to death Acastus' wife and, by some accounts, Acastus himself (Apollod. 3. 164–7, 173; schol. Ap. Rhod. 1. 224; cf. Paus. 3. 18. 16).