Atlas

Atlas is one of the Titans of Greek mythology, a race of primordial beings which predate the pantheon of Olympian gods.

Overview
When Zeus freed his siblings from their imprisonment within their father Cronus (who had swallowed them all to prevent them from fulfilling the prophecy that they would usurp his rule), the Gods embarked upon the great war in the heavens known as the Titanomachy. Unsurprisingly, Atlas chose to side with the Titans against the Gods, and when the Titans were ultimately defeated, most were exiled to Tartarus, the Greek equivalent of Hell. Zeus chose a special fate for Atlas, however, and sentenced him to forever hold up the sky as punishment.

Heracles
When demi-god Heracles was tasked with his twelve labours, one was to retrieve golden apples from the garden of Hera, which happened to be tended by some of Atlas’s daughters. Approaching Atlas, Heracles offered to take his burden for a time while Atlas fetched the apples from his offspring. Knowing that any who took his burden willingly would be forever condemned to bear it, Atlas attempted to trick Heracles upon his return by stating that he would deliver the apples to Zeus himself, if only Heracles would hold up the sky. Seeing through the ruse, Heracles pretended to agree, as long as Atlas would take the weight for a moment while he adjusted his cloak. When Atlas took the sky back, Heracles quickly snatched up the apples, and made his escape.

Trivia

 * A common misconception is that Atlas held the world on his shoulders, when in fact he was actually tasked with holding up the sky.