king of Parthia (reigned 211–191 BC) in southwestern Asia. In 209 he was attacked by the Seleucid king Antiochus III of Syria, who took Hecatompylos, the Arsacid capital (the present location of which is uncertain), and Syrinx in Hyrcania. Finally, however, Antiochus concluded a treaty with Artabanus, who after 206 lost much territory to Euthydemus, ruler of Bactria.