March 2, 1810–July 20, 1903

Pope Leo XIII (1810–1903) served as Supreme Pontiff of the Universal Church from 1878 until his death in 1903. His papacy enacted a grand program of renovation and expansion of the Catholic Church, firmly grounded in her “holy and venerable authority.”

The reign of Pope Leo XIII is the fourth-longest of any papacy in the two-thousand-year history of the Catholic Church. Over the course of a full quarter-century, Leo XIII courageously engaged with the modern world, asserting the Church’s authority and wisdom in the face of unprecedented challenges and confusion.

He was also a prolific author, issuing a total of eighty-six encyclical letters on matters both spiritual and social; of these, Cluny is proud to publish thirty-one in the two volumes of The Great Encyclicals of Pope Leo XIII.