Ardashir I or Ardeshir I (Middle Persian:, New Persian: اردشیر), also known as Ardashir the Unifier (180–242 AD), was the founder of the Sasanian Empire. He was the ruler of Estakhr since 206, subsequently Pars Province since 222, and finally "King of Kings of Sasanian Empire" in 224 with the overthrow of the Parthian Empire, ruling the Sasanian Empire until his death in 242. The dynasty ruled for four centuries, until it was overthrown by the Rashidun Caliphate in 651.