In Greek mythology, Aeson (/ˈiːsɒn/;^[1] Ancient Greek: Αἴσων Aísōn) was a king of Iolcus in Thessaly. He was the father of the hero Jason. According to one version of the story, he was imprisoned by his half-brother Pelias, and when Pelias intended to kill him he committed suicide. In another story, he was killed by Jason's wife Medea, who brought him back to life as a young man.

Aeson was the son of Cretheus and Tyro. He had two brothers Pheres and Amythaon. Through his mother Tyro who consorted with the sea god Poseidon, he had two half-brothers, Neleus and Pelias.^[2]

Aeson was the father of Jason and Promachus with Alcimede, daughter of Phylacus and Clymene.^[3][4][5][6] Other sources say the mother of his children was (1) Polymede^[7][8] or Polymele,^[9][10] or Polypheme^[11] a daughter of Autolycus, (2) Amphinome,^[12] (3) Theognete, daughter of Laodicus,^[11] (4) Rhoeo^[9] or (5) Arne^[13] or (6) Scarphe.^[13]

Pelias was power-hungry and he wished to gain dominion over all of Thessaly. To this end, he banished Neleus and Pheres and locked Aeson in the dungeons in Iolcus. Aeson sent Jason to Chiron to be educated while Pelias, afraid that he would be overthrown, was warned by an oracle to beware of a man wearing one sandal.

Many years later, Pelias was holding the Olympics in honor of Poseidon when Jason, rushing to Iolcus, lost one of his sandals in a river while helping Hera, in the form of an old woman, cross. When Jason entered Iolcus, he was announced as a man wearing one sandal. Suspicious, Pelias asked him what he (Jason) would do if confronted with the man who would be his downfall. Jason responded that he would send that man after the Golden Fleece. Pelias took that advice and sent Jason to retrieve the Golden Fleece.

During Jason's absence, Pelias intended to kill Aeson. However, Aeson committed suicide by drinking bull's blood. His wife killed herself as well, and Pelias murdered their infant son Promachus.^[14]

Alternatively, he survived until Jason and his new wife, Medea, came back to Iolcus. She slit Aeson's throat, then put his corpse in a pot and Aeson came to life as a young man. She then told Pelias' daughters she would do the same for their father. They slit his throat and Medea refused to raise him, so Pelias stayed dead.^[15]

• Medea draining the blood of Aeson in order to rejuvenate him
• Medea rejuvenates Aeson by Giuseppe Asioli (1811)
• Medea rejuvenates Aeson by Bartolomeo Guidobono (c. 1700)
• Medea Rejuvenating Eson by Domenicus van Wijnen (17th century)
• Medea Rejuvenating Aeson by Corrado Giaquinto (1760)