Catechism of the Catholic Church §2324 — excerpt
Intentional euthanasia, whatever its forms or motives, is murder. It is gravely contrary to the dignity of the human person and to the respect due to the living God, his Creator.
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.