Medusa was a Gorgon who lived with her two sisters Stheno and Euryale. Her hair was made of snakes and her gaze could turn people to stone.
Medusa and her sisters were the children of the ocean gods Phorcys and Cyto. Though she has variously been depicted as beautiful and terrifying to look at, she always features snakes in place of hair. It is said that she was once a beautiful golden-haired maiden and a priestess devoted to the goddess Athena, until she broke her vows and fell in love with Poseidon, the sea god. For this offense, she was cursed by Athena with serpentine hair and a petrifying gaze.
The hero Perseus was sent to retrieve Medusa's head by King Polydectes who wished to wed Perseus's mother. The gods helped Perseus on his quest: Hermes gave him his winged sandals, Athena provided him a mirrored shield, Hephaestus gave him a sword, and Hades offered a helmet that would turn Perseus invisible. Perseus used the shield to look at Medusa's reflection without being turned to stone, and used the sword to behead her. When she died, the winged horse Pegasus and the giant Chrysaor arose from her remains.
Medusa was the only Gorgon that was mortal and could thus be killed by Perseus.