Pope John VIII (Latin: Ioannes VIII) was Pope from 14 December 872 to his death in 882. He is often considered one of the ablest pontiffs of the 9th century.
He devoted much of his papacy attempting to halt and reverse the Muslim gains in southern Italy and their march northwards, which was "destroying the economy of papal patrimony." When his efforts to obtain assistance from either the Franks or the Byzantines was unavailing, John was forced to focus on strengthening the defenses of the city of Rome. To this end he reinforced the walls around the Vatican, and had defense works constructed at Saint Paul Outside the Walls.
Pope John supported Methodius in his mission to the Slavs, and defended him against the German episcopy, which felt that Methodius was intruding on their terrain. He authorized the translation of the Bible into Slavonic and extended diplomatic recognition to the Duchy of Croatia.