Despite doubt from some circles, there is strong evidence supporting the traditional belief that John, one of the twelve disciples, is author of the fourth gospel – which bears his name. The Gospel of John is believed to be the first of five New Testament books that he authored – which include three letters: First, Second, and Third John, and the book of Revelation.
Although John may have relied on earlier written sources for some of his information, it is believed he was an eyewitness to many of the events he describes.