John, son of Zebedee and younger brother of James the Greater, was a Galilean fisherman and one of the inner three disciples present at the Transfiguration and in Gethsemane. In the Synoptic Gospels and Acts he is a leading figure of the early community, paired repeatedly with Peter.
The Fourth Gospel never names him, but it repeatedly mentions an unnamed figure it calls the disciple whom Jesus loved, who reclines beside Jesus at the last supper, stands at the cross where the dying Jesus entrusts his mother to him, and reaches the empty tomb first. Early Christian tradition, from Irenaeus onward, identified that beloved disciple with John and treated him as the Gospel's author.
Modern scholarship is far more cautious. The identification is an inference the Gospel itself does not make, and the beloved disciple functions within the text as an ideal witness as much as a biographical person. What is not in doubt is that a distinctive body of early Christian writing, a Gospel, three letters and, by tradition, the Apocalypse, came to be gathered under his name, and the question of who actually wrote it has occupied the church and the academy alike.