Atlas was a Greek Titan, who was the son of Iapetus and Themis. He was the brother of Prometheus, Epimetheus, and Menoetius. In addition, he was also the father of the Pleiades and Hyades.
Atlas had many different roles in Greek mythology. He was a Titan who held up the sky. This means he supported heaven on his shoulders. In this role, he is often depicted holding up the celestial sphere on one shoulder while carrying a snake in his hand (or sometimes just wearing it as a crown).
Atlas was also credited with creating the constellations we see in the night sky today. This story is mentioned by Hesiod in his Theogony: “And Atlas through hard constraint upholds / The wide heaven with unwearied head.”
In another myth related to this idea, Atlas was punished by Zeus for stealing fire from Mount Olympus and giving it to humankind by being forced to hold up the heavens for eternity.
In some versions of this story, Atlas was turned into a mountain when Heracles (Hercules) came back from his 12 labors with Cerberus, the three-headed dog that guarded Hades (the underworld).
