Who wrote the Gospel of John in The Bible?

Critics are almost unanimous in believing that the Gospel
of John was written by John the apostle, who is refered to in the Gospels as "the
disciple whom Jesus loved." His name is not actually mentioned in the Gospel, which
would indicate that he himself had wrote it, as you wouldn't necessarily talk about
yourself by name if you are writing the story of somebody else. John the author
obviously had a high level of knowledge of Jewish life, as is seen by his references to
popular Messianic expectations and various other cultural references such as the
practice of circumcision and the animosity between Samaritans and Jews. In addition,
this Gospel contains details that point towards an eye-witness. One of the most cited
examples of this is the house of Bethany with the woman who annoints the feet of Jesus
in John 12:3:

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Then Mary took about a point of pure nard, an
expensive perfume; she poured it on Jesus' feet and wiped his feet with her hair. And
the house was filled with the fragrance of the
perfume.

Such detailed
touches point towards the account being written by somebody who was there, with Jesus.
Early writers such as Irenaeus and Tertullian argue that John wrote this Gospel, and
other critics have found nothing to argue to the contrary.