Parthia ( "Parθava"; "Parθaw"; "Pahlaw") is a historical region located in north-eastern Iran. It was conquered and subjugated by the empire of the Medes during the 7th century BC, was incorporated into the subsequent Achaemenid Empire under Cyrus the Great in the 6th century BC, and formed part of the Hellenistic Seleucid Empire following the 4th-century-BC conquests of Alexander the Great. The region later served as the political and cultural base of the Eastern-Iranian Parni people and Arsacid dynasty, rulers of the Parthian Empire (247 BC – 224 AD). The Sasanian Empire, the last state of pre-Islamic Iran, also held the region and maintained the Seven Parthian clans as part of their feudal aristocracy.