Micythus, son of Choerus, was a tyrant of Rhegium (modern Reggio Calabria) in the 5th century BC.
He was at first a slave in the service of Anaxilas, tyrant of Rhegium, but gradually rose to so high a place in the confidence of his master, that Anaxilas at his death (476 BC) left him guardian of his infant sons, with charge to hold the sovereign power in trust for them, until they should attain to manhood.
The administration of Micythus appears to have been both wise and vigorous, so that he conciliated the affections of his subjects, and held the government both of Rhegium and Messana, undisturbed by any popular commotions. One of the principal events of his reign was the assistance furnished by him to the Tarentines in their war against the Iapygians (473 BC), which was terminated by a disastrous defeat, in which 3000 of the Rhegians perished, and the fugitives were pursued by the barbarians up to the very gates of the city. But notwithstanding this blow, shortly after (471 BC) he was still powerful enough to found a new colony, the city of Pyxus, or Buxentum, as it was afterwards called.
It was from jealousy of Micythus that Hieron, tyrant of Syracuse, who had been on friendly terms with Anaxilas, was induced to invite the sons of that monarch, who were now grown up to manhood, to his court, urging them to require of their guardian the surrender of the sovereign power, as well as an account of his administration. But on the return of the young princes (467 BC), Micythus immediately complied with their request. And after rendering an exact account of the period of his rule, he resigned the supreme power and departed with all his private wealth to the Peloponnese, where he settled at Tegea, and resided there the rest of his life in honour and tranquillity.
He is also mentioned by Pausanias (who calls him Smicythus) as having distinguished himself by the number of statues and other offerings that he dedicated at Olympia.