In Greek mythology, Hesiod says that Medusa was the only mortal Gorgon.
Hesiod’s Theogony, composed in archaic Greece and usually dated to around the late eighth or early seventh century BCE, presents Medusa as one of three Gorgon sisters. Her sisters Stheno and Euryale are described as immortal, while Medusa alone can die. This distinction explains why Perseus can kill Medusa even though the other Gorgons survive.
The Theogony also places the Gorgons within a divine family descending from Phorcys and Ceto. Hesiod’s account is among the earliest surviving literary descriptions of their genealogy and fate.
Later authors, especially Ovid, added or reshaped major details about Medusa’s appearance and transformation. Readers should therefore distinguish Hesiod’s early genealogical account from later Roman versions of the myth.