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Bertha, Duchess of Brittany

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Bertha of Cornouaille (fl. 1125–56), also known as Bertha of Brittany (Breton: Berthe Breizh), was the Duchess of Brittany between 1148 until her death and Dowager Countess of Richmond. Bertha was the elder 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,[2] and she lived in England with Alan until his death in 1146. Alan would eventually become Earl of Richmond. On his deathbed, Conan III renounced Bertha's brother Hoel as heir[2] and designated Bertha as his heiress, Duchess of Brittany.[3]


In her first marriage, by 1138, Bertha was married to Alan the Black.[a]

Bertha and Alan had three children:

Bertha married her second husband, Odo, Viscount of Porhoet, in about 1148.[2][6] Bertha and Odo had three children:


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


  1. ^ Alan the Black 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.[4] The marriage between Bertha and Alan may have been intended to bring Brittany into the English civil war on the side of Stephen.
  2. ^ Everard states Odo and Bertha had only one daughter, Adelaide.[5]
  3. ^ War broke out between Bertha's son Conan IV, Duke of Brittany and her second husband Odo. 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. ^ Bryan 2016, p. 173.
  2. ^ a b c Warren 1977, p. 75.
  3. ^ a b Everard 2004, p. 149.
  4. ^ Cokayne, G. E., edited by H. A. Doubleday, Geoffrey H. White, & Lord Howard de Walden, The Complete Peerage, London, 1945, vol. x, p. 788.
  5. ^ a b c Everard 2004, p. 46.
  6. ^ Everard 2004, p. 32.
  7. ^ Vincent 2007, p. 331.


  • Bryan, Elizabeth J. (2016). "Matthew Parker and the Middle English Prose Brut". In Rajsic, Jaclyn; Kooper, Erik; Hoche, Dominique (eds.). The Prose Brut and Other Late Medieval Chronicles. York Medieval Press.
  • Dunbabin, Jean (1985). France in the Making, 843-1180. Oxford University Press.
  • Everard, J. A. (2004). Brittany and the Angevins: Province and Empire 1158–1203. Cambridge University Press.
  • Vincent, Nicholas (2007). "The Court of Henry II". In Harper-Bill, Christopher; Vincent, Nicholas (eds.). Henry II: New Interpretations. The Boydell Press.
  • Warren, Wilfred Lewis (1977). Henry II. Yale University Press.
Bertha, Duchess of Brittany
House of Cornouaille
Born: c. 1114 Died: 1156
Regnal titles
Preceded by Duchess of Brittany
Succeeded by