Mithridates or Mithradates VI Eupator (The spelling "Mithridates" was the Roman Latin version, but "Mithradates", the spelling used in Greek inscriptions and Mithridates' own coins, is regaining precedence, see e.g. Oxford Classical Dictionary, 3d ed. 135–63 BC) was the ruler of the Kingdom of Pontus in northern Anatolia from 120 to 63 BC, and one of the Roman Republic's most formidable and determined opponents.