John VIII, d. 882, pope (872–82), a Roman; successor of Adrian II. John strenuously opposed the activities of St. Ignatius of Constantinople in Bulgaria. When Ignatius died, John recognized Photius as patriarch and called the council (879–80) that momentarily reconciled the differences between East and West. John was deeply involved in imperial politics. He crowned Charles II (Charles the Bald) emperor and excommunicated the future Pope Formosus for opposition to his policy. When Charles II lost his power, John favored Charles the Fat, who became emperor as Charles III. The pope had to bribe the Saracens to keep them from entering Rome. He did much to root out corruption in the church in Rome, and, except for Nicholas I, he was the strongest pope of the 9th cent. He was assassinated by his own relatives. Marinus I succeeded him.

John VIII (John Palaeologus), 1390–1448, Byzantine emperor (1425–48), son and successor of Manuel II. When he acceded, the Byzantine Empire had been reduced by the Turks to the city of Constantinople. John sought in vain to secure Western aid by agreeing at the Council of Florence (1439) to the union of the Eastern and Western churches. His brother, Constantine XI, succeeded him in 1449 and was the last Byzantine emperor.