Gratian (died ca. 1155) is known as the father of canon law. His book on the laws of the Catholic Church revolutionized the study of canon law and was the single greatest authority on the subject until the 20th century.

Gratian was a monk in the Camaldolese congregation of the Order of St. Benedict. Hardly anything is known about his life. He was one of those historical figures whose works completely hide their persons. He was a lecturer at the monastery of Saints Felix and Nabor in Bologna in Italy at the time when that city was beginning to be widely known as a center for the study of law. The Catholic Church then had no uniform law. Over the centuries popes had made legal decisions, councils had issued decrees, and Church officials throughout Europe had used their authority in various ways. Doctrine and theology were also considered as...