Catechism of the Catholic Church §73 — excerpt
God has revealed himself fully by sending his own Son, in whom he has established his covenant for ever. the Son is his Father's definitive Word; so there will be no further Revelation after him.
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.