Rhadamanthus (also transliterated as Rhadamanthys or Rhadamanthos) in Greek mythology was a son of Zeus and Europa and brother of Minos, king of Crete and Sarpedon. He was raised by Asterion.

Driven out of Crete by his brother, Minos, who was jealous of his popularity, he fled to Boeotia, where he wedded Alcmene. Homer represents him as dwelling in the Elysian fields (Odyssey, iv. 564).

According to later legends, on account of his inflexible integrity he was made one of the judges of the dead in the lower world, together with Aeacus and Minos. He was supposed to judge the souls of Asians, Aeacus those of Europeans, while Minos had the casting vote (Plato, Gorgias, 424A).

Dante makes Rhadamanthus one of the judges of the damned in the Inferno section of Divine Comedy. "Rhadamanthine" has since come to describe any just but inflexible judgment.