one of the greatest generals of the ancient Achaemenid Empire of Persia.

He was the son of Zopyrus and the brother-in-law of King Xerxes I. Sent to quell an uprising in Babylon (482), Megabyzus quickly seized and devastated the city, carrying off the huge gold statue of Bel-Marduk. By melting down the statue, he thus prevented any future Babylonian ruler from legitimizing his position, which was done by grasping the hands of the god's image at the Babylonian Akitu (New Year) festival. Megabyzus accompanied Xerxes on his invasion of Greece, but he later became one of the co-conspirators in the assassination of Xerxes (465).

Under the new king, Artaxerxes I, Megabyzus was appointed satrap (governor) of Syria and was sent with a large army to restore Achaemenid rule in Egypt. Successful, he promised safety to Inaros, the leader of the Egyptian revolt, who thus surrendered. But after his pledge to Inaros was broken through the intrigues of the Achaemenid queen mother, Amestris, Megabyzus returned to Syria and rebelled. Although he and Artaxerxes became reconciled, he later offended the king on a hunting trip and was exiled to Cyrtae on the Persian Gulf. After five years he feigned leprosy and was allowed to return; through the intercession of the royal court, he and Artaxerxes became friends once more.