Franciscus Gratianus, or Johannes Gratianus, known most often simply as Gratian, was a 12th century canon lawyer from Bologna.

Since the 11th century, Bologna was 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, but he was probably born at the end of the 11th century, at Chiusi in Tuscany. He became a monk at the monastery of St. Felix in Bologna and devoted his life to studying canon law. His compilation, the Concordance of Discordant Canons, or the Decretum, was an attempt to logically solve apparently contradictory canons from previous centuries. He quoted other canons, the Bible, Augustine of Hippo, and other authorities in order to reconcile the laws. The Concordance was completed sometime after the Second Lateran Council, from which it quotes, possibly while Orlando Bandinelli was professor of canon law at the University of Bologna.

With later commentaries and supplements, the work was titled Corpus Juris Canonici, a conscious imitation of the Corpus Juris Civilis. The Decretum quickly became the standard text book for students of canon law throughout Europe.

The date of Gratian's death is not know, but he probably died before 1160.