(Βῆσσος), was satrap of Bactria in the time of Dareius III. (Codomannus), who saw reason to suspect him of treachery soon after the battle of Issus, and summoned him accordingly from his satrapy to Babylon, where he was collecting forces for the continuance of the war. (Curt. 4.6.1.) At the battle of Arbela, B. C. 331, Bessus commanded the left wing of the Persian army, and was thus directly opposed to Alexander himself. (Curt. 4.12.6; Arr. Anab. iii. p. 59e.) After this battle, when the fortunes of Dareius seemed hopelessly ruined, Bessus formed a plot with Nabarzanes and others to seize the king, and either to put him to death and make themselves masters of the emlpire, or to deliver him up to Alexander, according to circumstances. Soon after the flight of Dareius from Ecbatana (where, after the battle of Arbela, he had taken refuge), the conspirators, who had the Bactrian troops at their command, succeeded in possessing themselves of the king's person, and placed him in chains. But, being closely pressed in pursuit by Alexander, and having in vain urged Dareius to mount a horse and continue his flight with them, they filled up by his murder the measure of their treason, B. C. 330. (Curt. 5.9_13; Arr. Anab. iii. pp. 68, 69; Diod. 17.73; Plut. Alex. 42.) After this deed Bessus fled into Bactria, where he collected a considerable force, and assumed the name and insignia of royalty, with the title of Artaxerxes. (Curt. 6.6.13; Arr. Anab. iii. p. 71d.) On the approach of Alexander, he fled from him beyond the Oxus, but was at length betrayed by two of his followers, and fell into the hands of Ptolemy, whom Alexander had sent forward to receive him. (Curt. 7.5; Arr. Anab. iii. p. 75; comp. Strab. xi. p.513.) He was brought naked before the conqueror, and, having been scourged, was sent to Zariaspa, the capital of Bactria (Strab. xi. p.514) : here, a council being afterwards held upon him, he was sentenced to suffer mutilation of his nose and ears, and was delivered for execution to Oxathres, the brother of Dareius, who put him to a cruel death. The mode of it is variously related, and Plutarch even makes Alexander himself the author of the shocking barbarity which he describes. (Curt. 7.5, 10; Arr. Anab. iv. p. 82d.; Ptolem. and Aristobul. apud Arr. Anab. iii. ad fin.; Diod. 17.83; Plut. Alex. 43; Just. 12.5.)