In Greek mythology, Aegeus, also Aigeus, Aegeas or Aigeas, was the father of Theseus and an Athenian King. He was the son of Pandion and a brother of Pallas, Nisos, and Lykos.

Upon the death of Pandion, Aegeus and his brothers took control of Athens from Metion, who had seized the throne from Pandion. They divided the government in four but Aegeas became king. His first wife was Meta and the second was Chalciope.

Still without a male heir, Aegeus asked the Oracle at Delphi for advice. Her cryptic words were "Do not loosen the bulging mouth of the wineskin until you have reached the height of Athens."

Aegeus (king of Athens) went to Troezena and met with Aethra, daughter of Troezena's king Pittheus. Pittheus understood the prophesy and introduced Aegeas to his daughter, Aethra, when he was drunk. They had sex and then, in some versions, Aethra waded out to the sea to Sphairia and had sex with Poseidon). When she fell pregnant, Aegeus decided to go back to Athens. Before leaving, he covered his sandals, shield and sword under a huge rock and told her that when their son grew up, he should move the rock and bring the weapons back.

Theseus, the child, grew up and became a brave young man. He managed to move the rock and took his father's arms. His mother then told him the truth about who his father was and how he should take the weapons back to him. Theseus decided to go to Athens and had the choice of going by sea, which was the safe way or by land, following a dangerous path with thieves and bandits all the way. Young, brave and ambitious, Theseus decided to go to Athens by land.

When Theseus arrived, he did not reveal his true identity. He was welcomed by Aegeas, who was suspicious about the stranger who came to Athens. Aegeas' wife, Medea (who had fled from the wrath of Jason and had one son, Medus, with Aegeus), tried to have Aegeas kill Theseus by asking him to capture the Marathonian Bull, but Theseus succeeded. She tried to poison him but at the last second, Aegeas recognized the sandals, shield and sword and knocked the wine glass out of Theseus' hand. Father and son were reunited.

King Minos' son, Androgeus, lost every game in a contest to Aegeus of Athens. Alternatively, the other contests were jealous of Androgeus and killed him. Minos was angry and declared war on Athens. He offered the Athenians peace if, every year, they sent him seven young men and seven young women to feed to the Minotaur, a vicious monster. This continued until Theseus killed the Minotaur with the help of Ariadne, Minos' daughter.

Aegeus had told Theseus, before he left, to put up the white sails when he left Crete, if he had been successful in killing the Minotaur. Theseus forgot and Aegeus jumped into the sea when he saw the black sails coming into Athens, in the mistaken belief that his son had been slain. Henceforth, this sea was known as the Aegean Sea.

See also: Apollodorus. Bibliotheke; Catullus, LXIV; Plutarch. Theseus.