Odo, Count of Penthièvre
| Odo I | |
|---|---|
| Duke of Brittany, with Alan III | |
| Reign | 1008–1035 |
| Predecessor | Geoffrey I |
| Successor | Alan III by himself |
| Regent | Hawise of Normandy |
| Count of Penthièvre | |
| Reign | 1035–1079 |
| Successor | Geoffrey I |
| Regent of Brittany | |
| Reign | 1040–1057 |
| Born | c. 999 |
| Died | 7 January 1079 (aged c. 80) Cesson-Sévigné |
| Burial | |
| Spouse | Orguen-Agnes of Cornouaille |
| House | House of Rennes |
| Father | Geoffrey I |
| Mother | Hawise of Normandy |
Odo of Rennes (Medieval Breton: Eudon Pentevr, Modern Breton: Eozen Penteur, Latin: Eudo, French: Eudes/Éon de Penthièvre) (c. 999–1079), Count of Penthièvre, was the youngest of the three sons of Duke Geoffrey I of Brittany and Hawise of Normandy, daughter of Richard I of Normandy. Eudon married Agnes of Cornouaille (Orguen Kernev), the daughter of Alan Canhiart, Count of Cornouaille and sister of Hoel II, Duke of Brittany who was married in 1066 to Eudon's niece Hawise, Duchess of Brittany.