In Greek mythology, Aristodemus (Ancient Greek: Ἀριστόδημος) was one of the Heracleidae, son of Aristomachus and brother of Cresphontes and Temenus. He was a great-great-grandson of Heracles and helped lead the fifth and final attack on Mycenae in the Peloponnese.^[1]

Aristodemus and his brothers complained to the oracle^{[clarification needed]} that its instructions had proved fatal to those who had followed them; the oracle had told Hyllas to attack through the narrow passage when the third fruit was ripe. They received the answer that by the "third fruit" the "third generation" was meant, and that the "narrow passage" was not the isthmus of Corinth, but the straits of Rhium. They accordingly built a fleet at Naupactus, but before they set sail, Aristodemus was struck by lightning (or shot by Apollo) and the fleet destroyed, because one of the Heraclidae had slain an Acarnanian soothsayer.

His brothers were later able to conquer the Peloponnese.

By his wife Argia, daughter of King Autesion of Thebes, he was the father of twin kings Eurysthenes and Procles, the ancestors of the two royal houses of Sparta.^[2]