Catechism of the Catholic Church §2325 — excerpt
Suicide is seriously contrary to justice, hope, and charity. It is forbidden by the fifth commandment.
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.