The Gospel According to John is also referred to as the Gospel of John, the Fourth Gospel, or simply John.
"It is one of the four canonical gospels in the Christian Bible," Wikipedia notes. "In the New Testament it traditionally appears fourth, after the synoptic gospels of Matthew, Mark, and Luke. John begins with the witness and affirmation of John the Baptist and concludes with the death, burial, resurrection, and post-resurrection appearances of Jesus.
"Chapter 21 states that the book derives from the testimony of the 'disciple whom Jesus loved' and early church tradition identified him as John the Apostle, one of Jesus' Twelve Apostles. The Gospel is closely related in style and content to the three surviving Epistles of John such that commentators treat the four books, along with The Book of Revelation, as a single body of Johannine literature...."