Pope John XII (born 927)

Pope John XII, born Octavian, was the bishop of Rome and ruler of the Papal States from 16 December 955 to his death in 964. He was related to the counts of Tusculum, a powerful Roman family which had dominated papal politics for over half a century. He became Pope somewhere between the ages of 17 and 25. If he was 17 then he may have been the youngest Pope in history; if not, that title may belong to Benedict IX, who was between the ages of 11 and 20 when elected.