Mnemosyne — Classical Greek Myth Library

Cross-referenced catalogue index

Birth of Theseus: Aethra, Aegeus, and Poseidon (Double Paternity)

Catalogue ID: 03-heroes/043-birth-theseus-aethra-aegeus-poseidon-apollodorus

Cycle: Heroes — Theseus

Version line: Apollodorean / Plutarchan compilation (Trozenian conception; Aegeus and Poseidon both named as fathers)

Sources: Apollodorus, *Library* 3.15.7; *Epitome* 1.1–3; Plutarch, *Life of Theseus* 3–6

Source file: /workspace/greek-myth-catalogue/03-heroes/043-birth-theseus-aethra-aegeus-poseidon-apollodorus.md

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Aegeus, son of Pandion and king of Athens, had no child by any of his wives. Consulting the Delphic oracle about offspring, he received an obscure reply: not to loosen the projecting mouth of the wineskin until he reached the height of Athens, lest he die of grief. On his way home he stopped at Trozen and was entertained by Pittheus, son of Pelops. Pittheus understood the oracle, made Aegeus drunk, and put him to bed with his daughter Aethra. That same night Poseidon also lay with Aethra—or, in the Trozenian cult story preserved by Pausanias and folded into the biographical tradition, Athena bade Aethra go to the island of Sphairia (Holy Island) for a libation, and Poseidon overpowered her there. Thus Theseus was said to have two fathers: Aegeus by the mortal bed, Poseidon by the divine. Classical poets and Attic cult often treat him as son of the sea-god when his sea-power or underwater ordeal is at stake; Athenian civic legend equally insists on Aegeus’s blood so that the hero may inherit the Attic throne. Before leaving Trozen, Aegeus placed a sword and sandals under a great rock as tokens, and charged Aethra that if she bore a son who, when grown, could lift the rock, she should send him to Athens with the tokens, traveling by the safer sea if she could, and keep his parentage secret from the Pallantidai who threatened Aegeus’s house. Aethra bore Theseus and raised him at Trozen under Pittheus’s care. The boy grew strong and ambitious; when Heracles visited Trozen and laid aside his lion-skin, the other children fled, but Theseus attacked the skin with an axe, taking it for a living beast—an early sign of courage already circulating in the biographical tradition.