John 21:24-25

"This is the disciple who testifies of these things, and wrote these things; and we know that his testimony is true."

"And there are also many other things that Jesus did, which if they were written one by one, I suppose that even the world itself could not contain the books that would be written. Amen."

(The disciple spoken of is John here if you were unable to tell. Whether out of humility or another reason, John never mentions himself by name in this book once.)