The Greek god Atlas was one of the Titans, son of Japetus and Clymene and brother to Prometheus and Epimetheus.
He belongs to the generation of monstruous creatures that preceded the Olympians. For his participation in the fight between Titans and gods (the Titanomachia) he was punished by Zeus to hold apart heavens from Earth (note: he held the heavens, not the Earth, as we usually know).
There is a Roman statue from the 2nd century a.C., called "Atlante Farnese", in the Naples Museum (Italy), which is important because it represents for the first time the celestial sphere with all the constellations known at that time.
The Greek god Atlas (but in fact he was a Titan) was said to live in the country of the Hesperides, who were his daughters. When Hercules went after the Hesperides' apples, Atlas told him they wouldn't give those apples but to their father, so he would get them if only Hercules took his place for a little while. The Titan went after the golden apples and when he came back, he told Hercules he'd take them to Eurystheus himself, thus leaving him forever with that burden on his shoulders. Hercules understood he was tricked, so he decided to do the same: he told Atlas he agreed, but asked him to hold the heavens a little bit, until he puts a pillow on his shoulders, so as to feel more confortable. The Titan didn't realized it was the same trick, so he accepted, Hercules took the golden apples and off he went.
The hero Perseus, on the way back home after killing the Medusa, asked for hospitality, but the Greek god Atlas wouldn't let him stay, as he knew from goddess Themis that a son of Zeus would come to steal the golden apples from his garden. So Perseus took revenge, by showing him the Medusa's head and turning him into stone. His beard and his hair became a thick forest and his head became a high mountain peak. (Herodotus is the first one to mention a mount Atlas in Northern Africa)
- with Pleione: the Pleiades (Alcyone, Asterope, Celaeno, Electra, Maia, Merope and Taygeta) and the Hyades (in Roman mythology).
There was also another Atlas, the first son of the Greek god Poseidon and Clito, a young girl who lived beyond Hercules' Columns. Poseidon gave him the central mountain of this island, that's why the island was called (guessed already?) Atlantis. But this is another story!