Who was Medusa?

According to Greek mythology, Medusa was an immortal Gorgon monster; however, in later accounts she was described as a beautiful, young girl who was later turned into a monster by Athena who was jealous of her. Medusa is described as having snakes in place of hair and a demonic face.

Medusa was the daughter of Phorcys and Ceto. She had two other Gorgon sisters, Stheno and Euryale. Medusa was beheaded by the hero Perseus who kept her head, which had the power to turn anyone who looked at it directly into stone, and used it as a weapon. The head was later given to Athena who placed it on her shield or aegis.