III John is a book in the New Testament of the Christian Bible, also known as 3 John or Third John. There are several synonyms for III John, including the Third Epistle of John, the Third Letter of John, and the Third Book of John. While these synonyms refer to the same book, they may be used in different contexts or translations of the Bible. III John is a short letter written by the Apostle John to a man named Gaius, thanking him for his hospitality and encouraging him in his faith. It is a valuable source of insight into early Christian beliefs and practices.