John of Patmos

All that the book itself says of its writer is that his name was John, that he was a servant of Jesus Christ and a brother of those he wrote to, that he shared their suffering, and that he was on Patmos “because of God’s Word and the testimony of Jesus Christ” (Revelation 1:1, 9). He speaks of himself as one of the prophets (Revelation 22:8–9). He does not call himself an apostle or an elder, and he does not say more about why, or for how long, he was on the island.

Justin, in the middle of the second century, identified him as John the apostle (Justin, Dialogue with Trypho 81), and Irenaeus, about AD 180, placed the vision near the end of the reign of Domitian (Irenaeus, Against Heresies 5.30.3). In the third century Dionysius of Alexandria compared the Greek of the Revelation with that of John’s Gospel and concluded that they had different authors, both named John (Eusebius, Church History 7.25). Eusebius thought the writer might be the elder John whom Papias mentions (Eusebius, Church History 3.39.5–6). Eusebius also passes on the tradition that John was sent to Patmos in a persecution under Domitian and came back to Ephesus after the emperor’s death (Eusebius, Church History 3.18.1) (Eusebius, Church History 3.20).

This wiki keeps him apart from John the Apostle because the identification, though ancient, has been disputed since antiquity and is still disputed. See John’s Revelation on Patmos.