Duke of Penthièvre

In the 11th and 12th centuries the Countship of Penthièvre (Breton: Penteur) in Brittany (now in the department of Côtes-d'Armor) belonged to a branch of the sovereign House of Brittany. It initially belonged to the House of Rennes. Geoffrey I, Duke of Brittany, gave it to his brother Eudes in 1035, and his descendants formed a cadet branch of the ducal house.

The geographical region of Brittany that constituted the holdings of Penthièvre correlate closely with the territories that constituted the early Breton kingdom of Domnonée.

The history of the title Count of Penthièvre included frequent dispossessions and restorations. Henri d'Avaugour, heir of this family, was dispossessed of the countship in 1235. The Duke of Brittany, Pierre Mauclerc, founder of the Breton House of Dreux, gave it as dowry to his daughter, Yolande, on her marriage in 1238 to Hugh XI of Lusignan, Count of La Marche. John I, Duke of Brittany, Yolande's brother, seized the countship on her death in 1272. After the Breton War of Succession the title was dispossessed twice by the reigning Dukes of Brittany, once by John V and another time by Francis II.

In 1337 Joan the Lame, Duchess of Brittany, brought Penthièvre to her husband, Charles de Châtillon, Count of Blois. Joan was the daughter of Guy de Penthièvre, the brother of John III.

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