Artaxerxes III, d. 338 BC, king of ancient Persia (358–338 BC), son and successor of Artaxerxes II. He was originally named Ochus and is sometimes called Artaxerxes Ochus. He gained the throne by a general massacre of his brother's family, and throughout his reign he continued a policy of terror. An early expedition against Egypt failed (351 BC), but he set out again (c.342) and, having destroyed Sidon on his way, reduced Egypt by bloody conquest. He also put down the unruly satraps and centralized and strengthened the empire. One of his ministers, the eunuch Bagoas, finally poisoned the king, put Artaxerxes' son Arses on the throne in 338, then deposed him in 336 in favor of Darius III.