John I, Count of Penthièvre
| John I | |
|---|---|
| Count of Penthièvre | |
| Reign | 29 September 1364 – 16 January 1404 |
| Predecessor | Charles and Joan |
| Successor | Olivier |
| Born | 5 February 1345 Jurgon-les-Lacs, Brittany (France) |
| Died | 16 January 1404 Lamballe, Brittany |
| Spouse | Margaret de Clisson |
| Issue | Olivier John Charles d'Avaugour William de Limoges Joan, lady of Belleville |
| House | House of Châtillon |
| Father | Charles of Blois |
| Mother | Joan, Duchess of Brittany |
John I (5 February 1345 – 16 January 1404), was Count of Penthièvre and Viscount of Limoges from 1364 to 1404, and the Penthièvre claimant to the Duchy of Brittany.