In Greek mythology, Aegeus (Ancient Greek: Αἰγεύς Aigeús) or Aegeas (Αιγέας), was an archaic figure in the founding myth of Athens. The "goat-man" who gave his name to the Aegean Sea was, next to Poseidon, the father of Theseus, the founder of Athenian institutions and one of the kings of Athens.
Upon the death of the king, Pandion II, Aegeus and his three brothers, Pallas, Nisos, and Lykos, took control of Athens from Metion, who had seized the throne from Pandion. They divided the government in four and Aegeus became king.
Aegeus' first wife was Meta, and his second wife 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, lest you die of grief." Aegeus did not understand the prophecy and was disappointed.
This puzzling oracle forced Aegeus to visit Pittheus, king of Troezen, who was famous for his wisdom and skill at expounding oracles. Pittheus understood the prophecy and introduced Aegeus to his daughter, Aethra, when Aegeus was drunk. They lay with each other, and then in some versions, Aethra waded to the island of Sphairia (a.k.a. Calauria) and bedded Poseidon. When Aethra became pregnant, Aegeus decided to return to Athens. Before leaving, he buried his sandal, 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 to his father, who would acknowledge him. Upon his return to Athens, Aegeus married Medea, who had fled from Corinth and the wrath of Jason. Aegeus and Medea had one son named Medus.