Pope Marinus I

Pope Marinus I ( mə-RY-nəs; died 15 May 884) was the bishop of Rome and leader of the Papal States from 882 until his death on 15 May 884. Controversially at the time, he was already a bishop when he became pope, and had served as papal legate to Constantinople. He was also erroneously called Pope Martin II (Latin: Martinus II) leading to the second pope named Martin to take the name Martin IV.

Source: Wikipedia — https://en.wikipedia.org/wiki/Pope_Marinus_I