Cheiron (sometimes spelled Chiron) is a Centaur. Unlike the other Centaurs, however, he was immortal, a son of Cronus and Philyra. He trained many of the great heroes, such as Jason, Asclepius and Achilles, Peleus' son. When Peleus was left on Mt. Pelion (Chiron's home) to die, Cheiron befriends him. He returns to Peleus his sword, allowing him to fight off the other Centaurs.
Eventually, Cheiron is forced to flee from Mt. Pelion because of a war with the Lapiths.
He eventually settled in Malea, where he was accidentally wounded by the poisoned arrows of Heracles. In terrible pain, Cheiron wished for death. Still, he was immortal, and the pain continued. Only after Heracles persuaded Zeus to exchange him for Prometheus was Cheiron allowed to die.