Adiabene, petty kingdom that was a vassal state of the Parthian empire (247 bcad 224) in northern Mesopotamia (now Iraq). Its capital was Arba-ilu (Arbela; modern Irbīl). In the 1st century ad its royal family embraced Judaism; the queen mother Helena (d. ad 50), famous for her generosity to the Jews and the Temple, and her sons Monobazus II and Izates II were buried in the Tombs of the Kings at Jerusalem. Adiabene was frequently attacked by the Romans during their campaigns against the Parthians.