The first Sarpedon was a son of Zeus and Europa, and brother to Minos and Rhadamanthys. He was raised by King Asterion and then banished by Minos, and sought refuge with his uncle, King Cilix. Sarpedon conquered the Milyans, and ruled over them; his kingdom was named Lycia, after his successor, Lycus, son of Pandion II.
In another version, Minos, Sarpedon and Rhadamanthus quarreled over a beautiful boy they were all in love with, by the name of Miletus, son of Apollo and Areia. The youth however preferred Sarpedon, so Minos in revenge went to war and conquered the whole island. Sarpedon and his lover escaped to Lycia, where Miletus founded the city that bore his name. Other mythographers claimed that the beloved youth's name was Atymnios, and that he was the son of Zeus and Cassiopeia.(Apollodorus III.1.2)
Bernard Sergent claims that the story is a late invention in that the theme of competition for a beloved youth is not in keeping with the Cretan pederastic tradition, and there is no record of this Miletus prior to the second century BCE.
The second Sarpedon was a son of Zeus and Laodamia, daughter of Bellerophon, and also a Lycian King. Sarpedon became king when his uncles withdrew their claim to Lycia. He fought on the side of the Trojans, with his cousin Glaukos, during the Trojan War becoming one of Troy's greatest allies and heroes.
He scolded Hector in the Iliad claiming that he left all the hard fighting to the allies of Troy and not to the Trojans themselves and made the point to say that the Lycians had no reason to fight the Greeks, or no real reason to hate them, but because he was a faithful ally to Troy he would do so and fight his best anyway. When the Trojans attacked the newly built wall by the Greeks, Sarpedon led his division (Which also included Glaukos and Asteropaios) to the forefront of the battle and caused Ajax and Teucer to shift their attention from Hector's attack, to that of Sarpedon's forces. He personally held up the battlements and was the first to enter the Greek encampment. This attack allowed Hector to break through the Greek wall. It was during this action that Sarpedon delivered a noblesse oblige speech to Glaukos (12.310-28), stating that they had been the most honoured kings, therefore they must now fight the most to repay that honour and prove themselves and repay their loyal subjects. Charging into battle he told Glaukos that together they would go on to glory; if successful it would be their own if not it would add to the glory of whoever stopped them.
When Patroclus entered the battle in the armour of Achilles, Sarpedon met him in combat. Zeus debated on whether to spare his son's life even though he was fated to die by the hand of Patroclus. He would have done so had Hera not reminded him that other gods' sons were fighting and dying and other gods' sons were fated to die as well, if Zeus should spare his son of his fate another god may do the same, therefore Zeus let Sarpedon die while fighting Patroclus, but not before killing the only mortal horse of Achilles. During their fight Zeus sent a shower of bloody raindrops over the Trojans' heads expressing the grief for the impending death of his son.
When Sarpedon fell, mortally wounded, he called on Glaukos to rescue his body and arms. Patroclus withdrew the spear from Sarpedon that he embedded in him, and as it left Sarpedon's body his spirit went with it. A violent struggle then ensued over the body of the fallen king. The Greeks succeeded in gaining his armour (which was later given as a prize in the funeral games for Patroclus), but Zeus had Apollo rescue the corpse. Apollo took the corpse and cleaned it, then delivered it to Slumber and Death who took it back to Lycia for funeral honours.
One account holds that the first and second Sarpedon are both the same man, and that Zeus granted Sarpedon an extraordinary long life that had to end at the Trojan War. However, the favored account is that Sarpedon, brother of Minos, and Sarpedon, who fought at Troy, were two different men that lived generations apart. A genealogical link is provided between the two Sarpedons, through Laodamia. Laodamia is said to have married Evander, son of the first Sarpedon, and to have presented Evander with a son named Sarpedon (in reality her son by Zeus).
See: Iliad books: II, IV, XII, XVI.
There is also an asteroid named after the Trojan hero.
A third Sarpedon was a Thracian son of Poseidon, and brother to Poltys, King of Aenus. Unlike the other two Sarpedons, this Thracian Sarpedon was not a hero, but an insolent individual who was killed by Heracles.