Ivo of Kermartin was a 13th-century Breton priest and legal expert who served as a judicial vicar. Born in 1253 at a manor near Tréguier, he studied civil and canon law in Paris and Orléans. Known for his integrity, he frequently defended widows, orphans, and the impoverished, often refusing bribes and providing legal aid to those unable to pay. He lived a life of asceticism and devotion, eventually serving as a parish priest in Louannec, where he established a hospital to care for the sick.