Damisus (Greek: Δάμυσος) was a giant in Greek mythology, one of the sons of the earth (Gea) and of Uranus.
He was born, like his brothers, from the blood that flowed from the wound that Kronos had caused Uranus in order to avenge the Titans, locked up by Zeus in Tartarus. The Giants were huge, bearded, serpent-legged beings, and Damisus was the fastest.
Although of divine origin, they were mortal, but it took the union of a god and a mortal to kill a giant, Damisus having fallen under Zeus' lightning and Heracles' arrows. There was also a magical herb produced by the earth whose ingestion made them invulnerable to wounds inflicted by mortals.
To prevent the giants from having the light needed to find it, Zeus forbade the dawn, moon and sun to shine and in obscurity collected the plant. Damisus' body was buried in Palene where Chiron, Zeus' brother and the most famous of the centaurs, lived.
He was charged by Peleus with the education of his son Achilles after his mother Thetis tried to take away his human qualities by subjecting her son to the action of fire, injuring one of his legs. Chiron dug up Damysus, and replaced Achilles' bone with that of the giant, making Achilles an extraordinary runner.