Atlas was one of the Titans, son of Iapetus and Clymene, and brother of Prometheus, Epimetheus and Menoetius. During the Titanomachy, the War between the Titans and the Olympian gods, Atlas and his brother Menoetius sided with the Titans, while Prometheus and Epimetheus helped the Olympian gods. Atlas was the leader in the batttle; however, being on the losing side, Zeus condemned him to eternally stand on the western side of Gaea (the earth) holding Uranus (the sky) on his shoulders. Therefore, the contemporary depiction of Atlas holding the Earth on his shoulders is a misconception.
He was the Titan god of astronomy and navigation and he was married to his sister, Phoebe. He had numerous children, including the Hesperides, the Hyades, Hyas, the Pleiades, Calypso, Dione and Maera. He was associated with the Atlas mountains in northwest Africa. According to a later myth, when Perseus went to that region, a giant named Atlas tried to drive him away. So, Perseus revealed Medusa's head, whom he had already killed, thus turning Atlas into stone (the Atlas mountains themselves).
In the myth of the Twelve Labours of Heracles, the demigod was sent to bring the golden apples from Hera's garden, tended by the Hesperides and guarded by the dragon Ladon. Heracles asked Atlas to bring the apples to him; during that time, he would replace him in holding up the sky. Atlas went and brought the apples to Heracles; he then attempted to trick him into holding the skies forever. However, Heracles managed to evade the trick and left with the apples.