antipope from 997 to 998.

A monk of Greek descent whom the Holy Roman emperor Otto II named abbot of the monastery of Nonantola, Italy, he attained an influential position at the court of Otto's widow, the empress Theophano. In 988 Theophano made John bishop of Piacenza, Italy, later raising his see to an archbishopric. He was godfather of Theophano's son, the imperial prince Otto (Otto III) (III) and later king of Germany, who in 995 sent John to Constantinople as legate for his prospective marriage to a Byzantine princess. When Pope John XV died (March 996), Otto named his cousin Bruno ( Gregory V) as the successor. The Crescentii, a powerful Roman family, opposed Otto's choice, and while he was in Germany, Crescentius II led a revolt that usurped Gregory's office. John returned from Constantinople, and Crescentius, planning to ally Rome with Byzantium against Otto, offered John the papacy. Over the protests of his friend Abbot St. Nilus of Rossano, John accepted. In 997 the exiled Gregory excommunicated Crescentius. Otto brought an army to Italy the following year, and a reign of terror ensued. Otto captured both Crescentius and John. Crescentius was beheaded on April 29, and John, after having been blinded and mutilated, was either imprisoned or confined to a monastery. His life was spared through the intercession of Nilus.