Odo of Rennes (Breton: Eozen Penteur, French: Eudes/Éon de Penthièvre) (999–1079), Count of Penthièvre, was the youngest son of Duke Geoffrey I of Brittany and Hawise of Normandy, daughter of Richard I of Normandy. Following the death of his brother Duke Alan III, Eudes ruled as regent of Brittany in the name of his nephew Conan II, between 1040 and 1062, although some histories show 1057 as the year in which Conan II captures and imprisons him in chains. Eudes married Agnes of Cornwall, sister of Hoel II of Brittany. At least two of Eudes' sons (Alan and Brian) participated in the Norman conquest of England.
His children include:
His descendants became the junior branch of the Breton ducal family, which assumed control of the duchy in 1156 under Conan IV of Brittany.