Penitential canons are religious rules laid down by councils or bishops concerning the penances to be done for various sins. These canons, collected, adapted to later practice, and completed by suitable directions formed the nucleus of the Penitential Books (see Moral Theology).

They all belong to the ancient penitential discipline and retain only a historic interest; if the writers of the classical period continue to cite them, it is only as examples, and to excite sinners to repentance by reminding them of earlier severity. In a certain sense they survive, for the granting of indulgences is based on the periods of penance, years, day and quarantines. The penitential canons may be divided into three classes corresponding to the penitential discipline of the East, of Rome, or of the Anglo-Saxon Churches.