The last mentioned prophet in the Bible depends on which section you're referring to:
* Old Testament: The last prophet mentioned in the Old Testament is Malachi. The Book of Malachi is the last book in most canonical orderings of the Old Testament.
* New Testament: The last person referred to as a prophet in the New Testament is often considered to be John the Baptist. While he appears early in the Gospels, his ministry is understood as the culmination of the Old Testament prophetic tradition and the forerunner of Jesus. Some might also argue for figures mentioned in the Book of Revelation, which contains prophetic visions, but those figures are generally understood in symbolic rather than historical terms.