Third John is a short book in the New Testament of the Christian Bible, traditionally attributed to the Apostle John. It is one of the three letters known as the Johannine Epistles, which also include First John and Second John. The letter addresses a Christian named Gaius and commends him for his faithfulness and hospitality towards traveling missionaries. The main themes of Third John include the importance of supporting fellow believers and the dangers of pride and division within the church. The letter also mentions a man named Diotrephes, who refuses to welcome the missionaries and seeks to assert his authority, contrasting with Gaius's positive example.