Aeacus, in Greek mythology, son of Jupiter and Aegina, and first king of the island of Aegi-na. He was renowned for his justice, so that he was called upon to settle disputes not only among men, but even among the gods. His reputation was such that, on the occasion of an excessive drought in Greece, he was appointed by the oracle of Delphi to intercede with the gods for rain, and his prayers were successful. After his death, Pluto made him one of the three judges of Hades.