Catechism of the Catholic Church §719 — excerpt
John the Baptist is "more than a prophet." In him, the Holy Spirit concludes his speaking through the prophets. John completes the cycle of prophets begun by Elijah.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.