:For other figures with this name, see Gratian (disambiguation).Gratian, was a 12th century canon lawyer from Bologna. He is sometimes wrongly referred to as Franciscus Gratianus, or Johannes Gratianus, or Giovanni Graziano. His birth and death dates are unknown.

Since the 11th century, Bologna had been the centre of the study of canon law, as well as of civil law, after the Corpus Juris Civilis was rediscovered in western Europe. Little is known about Gratian's life. For a long time he was believed to have been born at the end of the 11th century, at Chiusi in Tuscany. He was said to have become a monk at Camaldoli and then he taught at the monastery of St. Felix in Bologna and devoted his life to studying canon law. Recent research has found no foundation for this view.

His compilation, the Concordia discordantium canonum (Concord of Discordant Canons), later simply named the Decretum, was an attempt, using early scholastic method, to solve seemingly contradictory canons from previous centuries. Gratian quoted a great number of authorities, including the Bible, papal and conciliar legislation, church fathers such as Augustine of Hippo, and secular law in his efforts to reconcile the canons. The vulgate version of Gratian's collection was completed at some point after the Second Lateran Council, which it quotes. Research by Anders Winroth, The Making of Gratian's Decretum , has shown that some manuscripts have survived of an early version of Gratian's text, which differs considerably from the mainstream textual tradition.

With later commentaries and supplements, the work was incorporated into the so-called Corpus Iuris Canonici. The Decretum quickly became the standard text book for students of canon law throughout Europe, but it never received any formal official recognition by the papacy. Only the Codex Iuris Canonici of 1917 put it out of use.Crompton (2006):174
Gratian was acclaimed as "The Father of Science of Canon law" and he later found a place in Dante's Paradise among the doctors of the Church.