Atlas (ăt'lus) [key], in Greek mythology, a Titan; son of Iapetus and Clymene and the brother of Prometheus. When the Titans were defeated, Atlas was condemned to hold the sky on his shoulders for all eternity—a mythical explanation of why the sky does not fall. Hercules shouldered the burden in exchange for Atlas fetching him the apples of the Hesperides. He is identified with the Atlas mountains in NW Africa. He was the father of Calliope and the Pleiades.