Aristobulus III of Judea (d. 35 BC) was the last scion of the Hasmonean royal house, brother of Herod's wife Mariamne, and paternal grandson of Aristobulus II. He was a favorite of the people on account of his noble descent and handsome presence, and thus became an object of fear to Herod, who at first sought to ignore him entirely by debarring him from the high priesthood. But his mother Alexandra, through intercession with Cleopatra and Mark Antony, compelled Herod to remove Hananel from the office of High Priest and appoint Aristobulus instead.

To secure himself against danger from Aristobulus, Herod instituted a system of espionage against him and his mother. This surveillance proved so onerous that they sought to gain their freedom by taking refuge with Cleopatra. Their plans were betrayed, however, and the disclosure had the effect of greatly increasing Herod's suspicions against his brother-in-law. As he dared not resort to open violence, he caused him to be drowned while he was bathing in Jericho.

This article was taken from the Jewish Encyclopedia (1903).