(Ἀλέξανδρος), the eldest son of ARISTOBULUS II., king of Judaea, was taken prisoner, with his father and brother, by Pompey, on the capture of Jerusalem (B. C. 63), but made his escape as they were being conveyed to Rome. In B. C. 57, he appeared in Judaea, raised an army of 10,000 foot and 1500 horse, and fortified Alexandreion and other strong posts. Hyrcanus applied for aid to Gabinius, who brought a large army against Alexander, and sent M. Antonius with a body of troops in advance. In a battle fought near Jerusalem, Alexander was defeated with great loss, and took refuge in the fortress of Alexandreion, which was forthwith invested. Through the mediation of his mother he was permitted to depart, on condition of surrendering all the fortresses still in his power. In the following year, during the expedition of Gabinius into Egypt, Alexander again excited the Jews to revolt, and collected an army. He massacred all the Romans who fell in his way, and besieged the rest, who had taken refuge on Mount Gerizim. After rejecting the terms of peace which were offered to him by Gabinius, he was defeated near Mount Tabor with the loss of 10,000 men. The spirit of his adherents, however, was not entirely crushed, for in B. C. 53, on the death of Crassus, he again collected some forces, but was compelled to come to terms by Cassius. (B. C. 52.) In B. C. 49, on the breaking out of the civil war, Caesar set Aristobulus at liberty, and sent him to Judaea, to further his interests in that quarter. He was poisoned on the journey, and Alexander, who was preparing to support him, was seized at the command of Pompey, and beheaded at Antioch. (J. AJ 14.5_7; Bell. Jud. 1.8, 9.)