Aegeus was the son of Pandion II, king of Athens, and Pylia, daughter of King Pylas of Megara, and thus, brother to Pallas, Nysus and Lykos. Aegeus' first wife was Meta, daughter of Hoples, and his second wife was Chalciope, daughter of Rhexenor, neither of whom bore him any children. At some point he married Autochthe, who bore him only daughters.
Still without a male heir, Aegeus asked the oracle at Delphi for advice. The cryptic words of the oracle 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 Aethra waded to the island of Sphairia (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.
When Aethra's son Theseus grew up, he found his father’s belongings left for him and went to Athens to claim his birthright. Aegeus recognized him as a son by his sword. Medea perceived Theseus to be a threat for Medus' inheritance, and tried to discredit and then to poison Theseus. When Aegeus discovered these schemes, he drove Medea out of Athens.
While visiting in Athens, King Minos' son, Androgeus, managed to defeat Aegeus in every contest during the Panathenaic Games. Out of envy, Aegeus sent him to conquer the Marathonian Bull, which killed him. Minos was angry and declared war on Athens. He offered the Athenians peace under the condition that Athens would send seven young men and seven young women every nine years to Crete to be fed to the Minotaur, a vicious monster. This continued until Theseus killed the Minotaur with the help of Ariadne, Minos' daughter. After his adventures in Crete, Theseus returned by ship to Athens. Aegeus previously had asked him to hang a white sail as a sign that he was alive, but Theseus neglected this request. When Aegeus saw Theseus’ ships return without a white sail, he assumed the worst and threw himself into the sea, which was named after him (Aegean Sea).