Aristobulus III of Judea (d. 35 BC) was the last scion of the Hasmonean
royal house, brother of Herod the Great'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).