Ivo of Chartres, Saint, c.1040-c.1116, French churchman, bishop of Chartres (after 1090). He was fearlessly outspoken and was briefly imprisoned for opposing the irregular second marriage of King Philip I of France. He worked to obtain a compromise in the struggle over investitures. His principal fame was for his knowledge of canon law. His Decretum and Panormia, collections of canons, were perhaps the most extensive until supplanted by the work of Gratian. In the prologue to these collections Ivo attempted to establish a hierarchy for the reconciliation of discordant laws, a system with methodological import for the rise of scholasticism. Feast: May 24.