Descriptions vary as to the winged stallion's birth and his brother the giant, Chrysaor; some say that they sprang from Medusa's neck as Perseus beheaded her, a "higher" birth, like the birth of Athena from the head of Zeus. Others says that they were born of the earth as Medusa's blood spilled onto it, in which case Poseidon would not be their sire. Athena caught and tamed Pegasus, and presented him to the Muses.
Hesiod connects the name Pegasos with the word for "spring, well", pēgē; everywhere the winged horse struck hoof to earth, an inspiring spring burst forth: one on the Muses' Mount Helicon, the Hippocrene ("horse spring"), at the behest of Poseidon to prevent the mountain swelling too much and another at Troezen. The actual etymology of the name is most likely from Luwian pihassas "lightning", or pihassasas, a weather god (the god of lightning). In Hesiod, Pegasos is still associated with this original significance by carrying the thunderbolts for Zeus.
Pegasus aided the hero Bellerophon, who is a double in some way for Perseus, in his fight against both the Chimera and the Amazons. There are varying tales as to how Bellerophon found Pegasus, some say that the hero found him drinking at the Pierian spring and that Polyidus told Bellerophon how to find and tame him, others that either Athena or Poseidon brought him to Bellerophon.
Prior to aiding Bellerophon, Pegasus brought thunderbolts to Zeus, and following Bellerophon's death he returned to Mount Olympus to aid the gods. In his later life, Pegasus took a wife, Euippe (or Ocyrrhoe) This family is the origin of the winged horses.
Pegasus was eventually turned into a constellation, but a single feather fell to the earth near the city of Tarsus (hence its name).