The authorship of the Book of John, specifically the Gospel of John, has been traditionally attributed to John the Apostle, also known as John the Beloved or John the Evangelist. Early Christian tradition, supported by figures such as Irenaeus and Polycarp, holds that John the Apostle wrote the gospel during his time in Ephesus around AD 85–95

. However, modern biblical scholarship debates this attribution. Many contemporary scholars argue that the Gospel of John was not written by John the Apostle himself, citing reasons such as the sophisticated Greek style and theological depth of the text, which seem inconsistent with the background of John as an uneducated Galilean fisherman. Instead, they suggest the gospel may have been written by an anonymous author or a Johannine community closely associated with John’s teachings

. The gospel itself does not name its author but refers to the writer as "the disciple whom Jesus loved," traditionally identified with John the Apostle

. Some scholars also propose that the gospel was dictated by John and transcribed by others, such as Andrew, based on historical commentary

. In summary:

• Traditional view: John the Apostle wrote the Gospel of John.
• Scholarly view: Authorship is uncertain; likely an anonymous author or Johannine community; John the Apostle’s direct authorship is questioned.
• Early church support: Irenaeus, Polycarp, and other church fathers affirm John the Apostle’s authorship.
• Modern critique: Differences in language, style, and theological content raise doubts about John the Apostle as the sole author

Thus, while John the Apostle is traditionally credited with writing the Book of John, the exact authorship remains debated among scholars.