Among the most famous encyclicals are Rerum novarum, issued by Pope Leo XIII in 1891, which addresses economic problems created by the Industrial Revolution and laid the foundation for modern Roman Catholic social teaching; Humanae vitae (“Of Human Life”), issued by Pope Paul VI’s in 1968, which rejects artificial contraception; and Laudato si’ (“Praise Be to You”), issued by Pope Francis in 2015, which addresses environmental concerns and treats care for the Earth as a moral issue of urgent concern.
In 2026 Leo XIV promulgated his first encyclical, Magnifica humanitas (“Magnificent Humanity”), which offers moral guidance on the use of artificial intelligence.