The Third Epistle of John, often referred to as Third John and written 3 John, is the antepenultimate book of the New Testament and attributed to John the Evangelist, traditionally thought to be the author of the Gospel of John and the other two epistles of John. The Third Epistle of John is a private letter composed to a man named Gaius, recommending to him a group of Christians led by Demetrius, which had come to preach the gospel in the area where Gaius lived. The purpose of the letter is to encourage and strengthen Gaius, and to warn him against Diotrephes, who refuses to cooperate with the author of the letter.