Mithridates of Cius (in Greek Mιθριδάτης or Mιθραδάτης; lived c. 386–302 BCE, ruled 337–302 BCE) a Persian noble, succeeded his kinsman or father Ariobarzanes II in 337 BCE as ruler of the Greek town of Cius in Mysia (today part of Turkey). Diodorus assigns him a rule of thirty-five years, but it appears that his rule of Cius was interrupted during that period. What circumstances led to his expulsion or subjection are unknown; nothing is heard of him until his death in 302 BCE. However, it appears that he had submitted to the Macedonian Antigonus, who, to prevent him from joining the league of Cassander and his confederates, arranged for his assassination in Cius.
According to Lucian, he was at least eighty-four years of age at the time of his death, which makes it likely that he is the same person as the Mithridates, son of Ariobarzanes, who in his youth circumvented and put to death Datames. King Mithridates I of Pontus was his kinsman, although it is not known whether he was his son.