pope from 931 to late 935 or early 936.

He was the son of Marozia (dominant lady of the Roman Crescentii family) perhaps by her reputed lover, Pope Sergius III. John was consecrated in February/March 931. He served his mother's political ends until 932/933, when his half-brother Alberic II (Marozia's son by Duke Alberic I of Spoleto), the self-proclaimed prince of Rome, deposed, arrested, and imprisoned her in Castel Sant'Angelo, Rome, and confined John to the Lateran. He remained a prisoner until his death.