abstract:Centesimus Annus (Latin for "hundredth year") is an encyclical which was written by Pope John Paul II in 1991 on the hundredth anniversary of Rerum Novarum, an encyclical issued by Pope Leo XIII in 1891. It is part of a larger body of writings, known as Catholic social teaching, that trace their origin to Rerum Novarum and ultimately the New Testament.