Atropatene, also known as Atropatia or Atropatian Media, was an ancient Iranian kingdom established in c. 323 BC by the Persian satrap Atropates. The kingdom, mostly centered around the present-day Azerbaijan region in northwestern Iran, was ruled by Atropates' descendants until the early 1st-century AD, when the Parthian Arsacid dynasty supplanted them. It was conquered by the Sasanians in 226, and turned into a province governed by a marzban ("margrave"). Atropatene was the only Iranian region to remain under Zoroastrian authority from the Achaemenids to the Arab conquest without interruption, aside from being briefly ruled by the Macedonian king Alexander the Great.