Bertha, Duchess of Brittany

Bertha of Cornouaille ( fl. 1125-55), also known as Bertha of Brittany (Breton: Berthe Breizh), was hereditary Duchess of Brittany between 1148 until her death[1] and Dowager Countess of Richmond. Bertha was the eldest daughter of Conan III of Brittany by Maude, the illegitimate daughter of King Henry I of England.[1] She was the last member of the Breton House of Cornouaille to reign over Brittany.


Bertha was the daughter of Duke Conan III of Brittany. She married the son of Stephen of Treguier, Alan the Black and she lived in England with Alan until his death in 1146. Alan would eventually become Earl of Richmond. After Alan's death she returned to Brittany as Dowager Countess of Richmond and eventually married Odo, Viscount of Porhoet. When her father Duke Conan III died, on his deathbed Conan III renounced Bertha's brother Hoèl as heir, [lower-alpha 1] and designated Bertha as his heiress. On Conan III's death she became hereditary Duchess of Brittany. [lower-alpha 2][1]


In her first marriage, by 1138, Bertha was married to Alan le Noir [lower-alpha 3] Bertha and Alan had three children:

Bertha married her second husband, Odo, Viscount of Porhoet in about 1148.[1] Bertha and Odo had three children:


Bertha died between 1158 and 1164, and with her death the ducal throne passed to her son Conan. [lower-alpha 4]


  1. Conan III renounced Hoèl as illegitimate and no son of his
  2. However, Hoel would remain as Count of Nantes.
  3. Alan le Noir was Count of Penthièvre. He was created 1st Earl of Richmond by Stephen of England for his support against the dispossessed Empress Matilda during the English Civil War.[1][2] The marriage between Bertha and Alan may have been intended to bring Brittany into the English Civil War on the side of Stephen.
  4. War broke out between Bertha's son Conan IV, Duke of Brittany and her second husband Odo.[1] Odo may have made a compact with his brother-in-law, Hoel of Nantes to divide Brittany between them. However in late 1156 Conan IV was able to defeat Odo and secure his maternal inheritance.


  1. 1 2 3 4 5 6 Brittany Genealogy extracted Feb 1, 2008
  2. Cokayne, G. E., edited by H. A. Doubleday, Geoffrey H. White, & Lord Howard de Walden, The Complete Peerage, London, 1945, vol. x, p. 788.
  3. 1 2 Cawley, Charles (12 June 2011), Brittany, Dukes & Nobility: Eudes (II) de Porhoët, Medieval Lands database, Foundation for Medieval Genealogy,
  4. Cawley, Charles (12 June 2011), Brittany, Dukes & Nobility: Alix de Porhoët, Medieval Lands database, Foundation for Medieval Genealogy,
Bertha, Duchess of Brittany
House of Cornouaille
Born: c. 1114 Died: 1156
Regnal titles
Preceded by
Conan III
Duchess of Brittany
Succeeded by
Conan IV
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