Atlas was born to the Titan Iapetus and the Oceanid Clymene, though some say his mother was Asia. His brothers were Prometheus, who later stole fire for mankind, Epimetheus, and Menoetius. When Zeus and the young Olympian gods rose up against the older generation of Titans in a war called the Titanomachy, Atlas fought on the side of the Titans. The war lasted ten years and shook the cosmos to its foundations. When the Titans finally fell, Zeus punished those who had opposed him. While some were cast into the dark pit of Tartarus, Atlas received a unique and unending sentence. He was sent to the western edge of the world and forced to hold up the broad sky upon his shoulders, standing forever as a pillar to keep heaven and earth from collapsing into one another.

At the edge of the world, Atlas also tended the garden of his daughters, the Hesperides, where a tree of golden apples grew. These apples were sacred to the goddess Hera, and the garden lay in the far west where Atlas stood. Many years later, the hero Heracles arrived during his eleventh labor, a series of impossible tasks he had been forced to complete. He had been sent to fetch the golden apples, but the tree was guarded by a serpent and the daughters themselves. Heracles found Atlas still bearing the sky and offered a deal: he would hold the heavens for a while if Atlas would fetch the apples himself. Atlas agreed, and for a brief moment the Titan was free. He returned with the apples, but then refused to take the burden back, declaring that he would deliver the apples himself and leave Heracles holding the sky forever. Heracles, forced to use cunning where strength had failed, pretended to agree and asked Atlas to hold the sky just a moment longer while he padded his shoulders with a cushion. The moment Atlas took the weight back, Heracles seized the apples and fled, leaving the Titan condemned once more.

In another tale, the hero Perseus flew past Atlas's realm carrying the severed head of the Gorgon Medusa, a creature so terrible that one look at her face turned living things to stone. Atlas, remembering an ancient prophecy that a son of Zeus would one day steal his golden apples, tried to drive Perseus away. Perseus, unable to match the Titan's strength, raised the Gorgon's head. Atlas froze where he stood, his body turning to solid stone in an instant. His petrified form became a vast mountain range that stretched across northwestern Africa, and the peaks were said to hold up the edge of the sky itself. To this day, the Atlas Mountains bear his name.

Centuries later, the image of Atlas holding a sphere was misunderstood. Artists began to show him carrying the Earth itself rather than the heavens. In the sixteenth century, the Flemish geographer Gerardus Mercator used the Titan's name for his collection of maps, and ever since, a book of maps has been called an atlas.