One etymology suggests the name derives from the Ancient Greek words for "projectile" or "dart" (bélos / belóne) combined with "-phóntēs" (slayer). Geoffrey Kirk, however, proposes that "Bellerophontes" means "slayer of Belleros," referring to a Corinthian citizen accidentally killed by Bellerophon while he was practicing knife-throwing, which forced his exile to Lycia. This origin parallels the way Hermes gained the epithet Argeiphontes ("slayer of Argus") after killing Argus Panoptes.

Some scholars suggest that Belleros may have been a local Lycian daimon, as Bellerophon's name invited all sorts of speculation. Only two Byzantine scholars — John Tzetzes and Eustathius of Thessalonica — mention this Belleros figure, apparently following the name-etymology itself.

Robert Graves proposed an etymology by way of "beleēphoron," interpreted as "bearing darts," while Joseph T. Shipley interprets the name as "slayer of monsters."

Bellerophon was the son of the mortal Eurynome (or Eurymede) and Poseidon, and was raised by his foster father Glaucus. He had a brother named Deliades, who is also called Peiren or Alcimenes.

Bellerophon fathered three children with Philonoe, daughter of King Iobates of Lycia: Isander (Peisander), Hippolochus, and Laodamia (also named Deidamia or Hippodamia). Philonoe was also known as Alkimedousa, Cassandra, Anticleia, or Pasandra. In some accounts, Bellerophon also fathered Hydissos by Asteria, daughter of Hydeus.

Bellerophon's journey begins with exile, following either the accidental murder of his brother or the slaying of a Corinthian nobleman called "Belleros" or "Belleron" during knife-throwing practice. This act resulted in his name being changed from Hipponous to Bellerophon.

To atone, he appealed to Proetus, king of Tiryns in the Argolid. Though Proetus cleansed him of the crime, the king's wife — either Anteia or Stheneboea — attempted to seduce Bellerophon. When he rejected her, she falsely accused him of assaulting her instead. Proetus, bound by the sacred law of xenia (guest-friendship), could not kill a guest directly. Instead, he sent Bellerophon to King Iobates of Lycia, Proetus's father-in-law in the plain of the River Xanthus, bearing a sealed tablet that read: "Please remove this bearer from the world: he attempted to violate my wife, your daughter."

Iobates feasted with Bellerophon for nine days before reading the tablet. Fearing the wrath of the Erinyes for murdering a guest, Iobates instead sent Bellerophon on an apparently impossible quest: to kill the Chimera, a fire-breathing monster with a goat's body, lion's head, and serpent's tail that dwelt in neighboring Caria.

On his way to Caria, Bellerophon encountered the famous Corinthian fortune teller Polyeidos, who advised him that he would need the mythical Pegasus to emerge victorious.

Polyeidos instructed Bellerophon to sleep in Athena's temple. In a dream, Athena placed a golden bridle beside him, saying: "Sleepest thou, prince of the house of Aiolos? Come, take this charm for the steed and show it to the Tamer thy father as thou makest sacrifice to him of a white bull."

Upon waking, Bellerophon found the bridle was real. Polyeidos directed him to approach Pegasus while it drank from the never-failing Pirene spring on Corinth's citadel — Bellerophon's birthplace. He successfully mounted Pegasus and flew to Lycia to face the Chimera.

Alternative accounts state that Athena brought Pegasus already tamed and bridled, or that Poseidon, secretly Bellerophon's father and the horse-tamer, delivered Pegasus, as Pausanias understood.

Upon arriving in Lycia, Bellerophon found that he could not harm the Chimera despite riding Pegasus. When he felt the beast's hot breath, inspiration struck. He fastened a large block of lead to his spear and flew directly at the Chimera, lodging the lead deep in its throat. The fire-breath melted the lead, which then blocked the creature's airway and suffocated it. Some red-figure pottery depicts Bellerophon wielding Poseidon's trident instead of a spear.

When Bellerophon returned victorious to King Iobates, the king disbelieved the story and assigned a series of daunting quests. Bellerophon defeated the warlike Amazons by dropping boulders from his winged horse. In some versions, he first faced the Solymi.

Against a Carian pirate named Cheirmarrhus, Iobates' men attempted an ambush but failed when Bellerophon killed every assassin sent against him. When palace guards advanced, Bellerophon called upon his father Poseidon, who flooded the Xanthus plain behind him. The palace women rushed from the gates with their robes lifted high to expose themselves; unwilling to confront undressed women, Bellerophon withdrew.

Iobates relented, produced the original letter, and permitted Bellerophon to marry his daughter Philonoe. He granted Bellerophon half his kingdom, with its vineyards and grain fields. Philonoe bore Isander (Peisander), Hippolochus, and Laodamia, who later slept with Zeus and bore Sarpedon but was slain by Artemis.

Bellerophon took revenge on Stheneboea and Proetus. After returning following the Chimera's death, he feigned reciprocating Stheneboea's love. He promised to take her away to Caria, and she eagerly followed him on Pegasus. While flying over Milos, Bellerophon threw her from the horse, and she drowned in the waves below. Fishermen recovered her body, and Bellerophon confessed his actions to Proetus, claiming he had exacted appropriate justice through her death and his grief.

As Bellerophon's fame grew, so did his hubris. Believing that his victory over the Chimera entitled him to visit Mount Olympus, he attempted to fly there on Pegasus. This angered Zeus, who sent a gadfly to sting Pegasus, causing Bellerophon to fall back to Earth and die. Pegasus completed the flight to Olympus, where Zeus used him as a pack horse for his thunderbolts.

According to alternative narratives, Bellerophon was blinded after falling into a thorn bush on the Plain of Aleion ("Wandering") in Cilicia, where he lived out his remaining years in misery, "devouring his own soul," until death.

Approximately thirty quotations from Euripides' lost tragedy Bellerophon survive in other texts, allowing scholars to assess its theme: the tragic consequences of attempting to storm Olympus on Pegasus. One notable passage shows Bellerophon doubting the gods' existence, owing to the contrast between the wicked living easily while the good suffer. This seemingly "atheistic" position led Aristophanes to accuse Euripides himself of atheism.

The replacement of Bellerophon by the more familiar culture hero Perseus represents a development of Classical times that became standardized during the Middle Ages and was subsequently adopted by European Renaissance poets and their successors.