In Greek mythology, Medusa (mᵻˈdjuːzə,_-sə; Médousa), also called Gorgo, was one of the three Gorgons. Medusa is generally described as a human female with living venomous snakes in place of hair; those who gazed into her eyes would turn to stone. Most sources describe her as the daughter of Phorcys and Ceto, although the author Hyginus makes her the daughter of Gorgon and Ceto.
Medusa was beheaded by the Greek hero Perseus, who then used her head, which retained its ability to turn onlookers to stone, as a weapon until he gave it to the goddess Athena to place on her shield. In classical antiquity, the image of the head of Medusa appeared in the evil-averting device known as the Gorgoneion.
According to Hesiod and Aeschylus, she lived and died on Sarpedon, somewhere near Cisthene. The 2nd-century BC novelist Dionysios Skytobrachion puts her somewhere in Libya, where Herodotus had said the Berbers originated her myth as part of their religion.
The three Gorgon sisters—Medusa, Stheno, and Euryale—were all children of the ancient marine deities Phorcys (or "Phorkys") and his sister Ceto (or "Keto"), chthonic monsters from an archaic world. Their genealogy is shared with other sisters, the Graeae, as in Aeschylus's Prometheus Bound, which places both trios of sisters far off "on Kisthene's dreadful plain":
Near them their sisters three, the Gorgons, winged
With snakes for hair—hatred of mortal man
While ancient Greek vase-painters and relief carvers imagined Medusa and her sisters as having monstrous form, sculptors and vase-painters of the fifth century BC began to envisage her as being beautiful as well as terrifying. In an ode written in 490 BC, Pindar already speaks of "fair-cheeked Medusa".
In a late version of the Medusa myth, by the Roman poet Ovid, Medusa was originally a beautiful maiden, but when Neptune (the Roman equivalent of the Greek Poseidon) had sexual intercourse with her in Minerva's temple (Minerva being the Roman equivalent of the Greek Athena), Minerva punished Medusa by transforming her beautiful hair into horrible snakes.