Pegasus is a legendary winged horse in Greek mythology. Sired by the ocean god Poseidon, this noble beast was birthed by the gorgon Medusa when she was slain by the hero Perseus. Greco-Roman poets write about his ascent to heaven after his birth and his obeisance to Zeus, king of the gods, who instructed him to bring lightning and thunder from Olympus. Friend of the Muses, Pegasus is the creator of Hippocrene, the fountain on Mt. Helicon.
He was captured by the Greek hero Bellerophon near the fountain Peirene with the help of Athena and Poseidon. Pegasus allows the hero to ride him to defeat a monster, the Chimera, before realizing many other exploits. His rider, however, falls off his back trying to reach Mount Olympus. Zeus transformed him into the constellation Pegasus and placed him up in the sky.
In modern times, Pegasus has been popularised in many forms of media, many of which feature numerous winged horses referred to as pegasus (plural: pegasi).