Erechtheus (ĕrĕk´thēəs), in Greek mythology, king of Athens. On the advice of an oracle he sacrificed one of his daughters during the battle between the Athenians and the Eleusinians. This enabled him to win the battle, but Poseidon later destroyed him and all his house. Erechtheus is often confused with Erichthonius, his grandfather. Both were associated with the worship of Athena; one or the other is said to have built a temple which was the forerunner to the Erechtheum built in the 5th cent. BC, and to have established the Panathenaea (see Athena).