House of Dreux-Montfort

Montfort of Brittany
Arms of the Montfort Dukes of Brittany
Country	France
Estates	Brittany
Parent house	House of Dreux
Titles	Duke of Brittany
Founded	1322
Founder	John of Montfort
Final ruler	Anne of Brittany
Dissolution	1514
Ethnicity	Breton, French

The House of Montfort was a French noble family, which reigned in the Duchy of Brittany from 1365 to 1514. It was a cadet branch of the House of Dreux; it was thus ultimately part of the Capetian dynasty. It should not be confused with the older House of Montfort which ruled as Counts of Montfort-l'Amaury.

It succeeded the Brittany branch of the House of Dreux, invoking already in 1341 a right to succeed John III, Duke of Brittany. A war ensued, ultimately won by Montforts in 1364.

The dynasty was succeeded by Valois family, first Claude, the daughter of Montfortine duchess Anne, and then Claude's sons. Already from the time of Duchess Anne's marriage, however, the duchy was gradually subsumed to the French state, in practice, so it can be said that French central government succeeded the Montforts.

Count John of Montfort (1295–1345) was the sole surviving son of Yolande of Dreux, Countess of Montfort suo jure (and dowager queen of Scotland) from her second marriage to Arthur II, Duke of Brittany. John inherited in 1322 Montfort-l'Amaury from his mother. However, he was only a younger son of the Duke, who had several older sons from his first marriage. John only received some appanage in Brittany, and his maternal inheritance, a countship, was a much more important possession.

However, his eldest half-brother, John III, Duke of Brittany, was childless in spite of his three marriages. Duke John III died in 1341, and his duchy's nobles proclaimed Countess Joan of Dreux reigning duchess. She was the daughter of the late Guy, Count of Penthièvre, Duke John III's younger full brother, and thus John III's full niece.

John of Montfort however invoked both the principle of Salic law (allowing only males to succeed) and the principle of proximity of blood (as used earlier, e.g. by John of England against Arthur I of Brittany), having himself proclaimed Duke. This led to the Breton War of Succession, a part of the Hundred Years' War. His patron in this quest was king Edward III of England. The rivals, Duchess Joanna and her husband Charles of Blois were supported by the Valois kings of France. John of Montfort died without accomplishing his objective of becoming sole ruler of Brittany, but his wife Joanna of Flanders continued the fight in the name of their son John IV, Duke of Brittany (1339/40–99) who ultimately got the upper hand in the strife.