Pegasus

"In Greek mythology, Pegasus is the winged horse that was fathered by Poseidon with Medusa. When her head was cut of by the Greek hero Perseus, the horse sprang forth from her pregnant body. His galloping created the well Hippocrene on the Helicon (a mountain in Boeotia).

"When the horse was drinking from the well Pirene on the Acrocotinth, Bellerophon's fortress, the Corinthian hero was able to capture the horse by using a golden bridle, a gift from Athena. The gods then gave him Pegasus for killing the monster Chimera but when he attempted to mount the horse it threw him off and rose to the heavens, where it became a constellation (north of the ecliptic).

"In another version, Bellerophon killed the Chimera while riding on Pegasus, and when he later attempted to ride to the summit of Mount Olympus, Zeus sent a gadfly to sting the horse, and it threw Bellerophon off its back."

-- Source unknown