Danaüs (dăn´āəs), in Greek mythology, son of Belus and Anchinoe and twin of Aegyptus. Danaüs, who had 50 daughters, the Danaïds, and Aegyptus, who had 50 sons, ruled Libya and Arabia. When Belus died the brothers quarreled, and Danaüs fled with his daughters to Argos in Greece. There he became so powerful a ruler that the Greeks called themselves the Danai after him. Nevertheless, Aegyptus' sons pursued them and besieged Argos, demanding the Danaïds in marriage. Danaüs, forced to consent, instructed his daughters to kill their husbands on the wedding night. All obeyed but one; Hypermnestra spared Lynceus, who in some versions of the legend killed Danaüs and became king himself. For their crime the other Danaïds were condemned in Hades to the eternal task of filling a sieve with water. The Suppliants of Aeschylus is the first and only extant play of a trilogy dealing with the daughters of Danaüs.