Calais and Zetes, in Greek mythology, the winged twin sons of Boreas and Oreithyia. On their arrival with the Argonauts at Salmydessus in Thrace, they liberated their sister Cleopatra, who had been thrown into prison by her husband, Phineus, the king of the country. According to Apollonius of Rhodes (Argonautica, Book II), they delivered Phineus from the Harpies. They were slain by Heracles near the island of Tenos because they had persuaded the Argonauts to sail on without Heracles when he went to look for his lover, Hylas, in Mysia. Calais traditionally founded Cales in Campania.