Castī Connūbiī (Latin: "of chaste wedlock") was a papal encyclical promulgated by Pope Pius XI on December 31, 1930. It stressed the sanctity of marriage, prohibited Roman Catholics from using any form of artificial birth control, and reaffirmed the prohibition on abortion. It also explained the authority of Church doctrine on moral matters, and advocated that civil governments follow the lead of the Church in this area.