| Guy of Thouars | |
| Succession: | Duke of Brittany |
| Reign: | 1199–1201 |
| Predecessor: | Constance and Arthur I |
| Pre-Type: | Predecessors |
| Successor: | Arthur I |
| Regent: | Constance and Arthur I |
| Reg-Type: | Co-rulers |
| Succession1: | Regent of Brittany |
| Reign1: | 1203–1206 |
| Reign-Type1: | Regency |
| Regent1: | Alix |
| Reg-Type1: | Monarch |
| House: | Thouars |
| Father: | Geoffroy IV of Thouars |
| Mother: | Aénor de Lusignan |
| Spouses: | |
| Issue: |
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| Death Place: | Chemillé |
Guy of Thouars (died 13 April 1213) was Duke of Brittany from 1199 to 1201 as the third husband of Constance, Duchess of Brittany. They married in Angers, County of Anjou, between August and October 1199[1] after her son Arthur entered Angers to be recognized as count of the three countships of Anjou, Maine and Touraine. He was an Occitan noble, a member of the House of Thouars.
Between 1196 and the time of her death in 1201, while delivering twin daughters, Constance ruled Brittany with her young son, Arthur I, as co-ruler. Duke Arthur was captured in 1202 by his uncle John, King of England, and disappeared in 1203. Arthur's elder full sister Eleanor, was captured along with him and imprisoned by John. Arthur was succeeded by his infant half-sister, Guy's daughter Alix of Thouars. Guy served as regent of Brittany for his daughter from 1203 to 1206.
In 1204, Guy as regent of Duchess Alix, vassal of Philip II of France, undertook the siege of the Norman island fortress of Mont Saint-Michel. Because the abbey would not surrender, he set fire to the village and massacred the population. He was obliged to beat a retreat under the powerful walls of the abbey. The fire which he himself lit extended to the buildings, and the roofs were engulfed in flames. Philip II paid Abbot Jordan for the reconstruction cost.
In 1206 Philip II took the regency of Brittany himself, much to the consternation of the Breton nobles.
Guy died in 1213 in Chemillé in the county of Maine, and was buried with Constance at Villeneuve Abbey, now in the commune of Les Sorinières, outside of Nantes. 'Situated at Nantes south gate, Abbey de Villeneuve' was 'founded in 1201 by Constance de Panthièvre, the Duchess of Brittany ...'[2]
Guy married Constance of Brittany in 1199.[3] They had two or three[4] daughters:
Guy remarried Eustachie of Chemillé in 1203. They had two sons: