The Duchy of Brittany was a medieval feudal state that existed between approximately 939 and 1547. Its territory covered the northwestern peninsula of Europe, bordered by the Atlantic Ocean to the west, and the English Channel to the north. It was also less definitively bordered by the river Loire to the south, and Normandy, and other French provinces, to the east. The Duchy was established after the expulsion of Viking armies from the region around 939. The Duchy, in the 10th and 11th centuries, was politically unstable, with the dukes holding only limited power outside their own personal lands. The Duchy had mixed relationships with the neighbouring Duchy of Normandy, sometimes allying itself with Normandy, and at other times, such as the Breton-Norman War, entering into open conflict.
Geoffrey I, also known as Geoffrey of Rennes and Geoffrey Berengar, was the eldest son of Duke Conan I of Brittany. He was Count of Rennes, by right of succession. In 992 he assumed the title of Duke of Brittany, which had long been an independent state, but he had little control over much of Lower Brittany.
Odo of Rennes, Count of Penthièvre, was the youngest of the three sons of Duke Geoffrey I of Brittany and Hawise of Normandy, daughter of Richard I of Normandy. Eudon married Agnes of Cornouaille, the daughter of Alan Canhiart, Count of Cornouaille and sister of Hoel II, Duke of Brittany who was married in 1066 to Eudon's niece Hawise, Duchess of Brittany.
Conan II of Rennes was Duke of Brittany, from 1040 to his death. Conan was the eldest child and heir of Alan III, Duke of Brittany by his wife Bertha of Blois, and member of the House of Rennes. He was the elder brother of Hawise, who succeeded him as suo jure duchess.
Hoël II was Count of Kernev, from 1058 as Hoël V. On the basis of his marriage to Hawise, Duchess of Brittany, in 1066, he became Duke of Brittany jure uxoris.
Alan IV was Duke of Brittany from 1072 until his abdication in 1112. He was also Count of Nantes and Count of Rennes. His parents were Duchess Hawise and Duke Hoel II. He is also known as Alan Fergant. Through his father, he was of the Breton House of Cornouaille dynasty. He was the last Breton-speaking Duke of Brittany.
Conan III, also known as Conan of Cornouaille and Conan the Fat was duke of Brittany, from 1112 to his death. He was the son of Duke Alan IV and Ermengarde of Anjou.
Hoèl of Cornwall was count of Nantes, from 1148 to his death. He was raised the son of Duke Conan III and Maud FitzRoy, an illegitimate daughter of King Henry I of England. However, he was disinherited by his father when on his death-bed, as Conan III claimed that Hoèl was illegitimate and no son of his. Bertha then became heiress to Duke Conan's lands in Brittany, while Hoèl was allowed to remain Count of Nantes. He was accused by St. Bernard of Clairvaux of having an incestuous affair with his sister Bertha.
Odo II, Count of Porhoet was the son of Geoffroy, Viscount de Porhoët, and his wife Hawise. He became Duke of Brittany in 1148, jure uxoris, upon his marriage to Bertha, Duchess of Brittany.
Conan IV, called the Young, was the Duke of Brittany from 1156 to 1166. He was the son of Bertha, Duchess of Brittany, and her first husband, Alan, Earl of Richmond. Conan IV was his father's heir as Earl of Richmond and his mother's heir as Duke of Brittany. Conan and his daughter Constance would be the only representatives of the House of Penthièvre to rule Brittany.
The now-extinct title of Earl of Richmond was created many times in the Peerage of England. The earldom of Richmond was initially held by various Breton nobles; sometimes the holder was the Breton duke himself, including one member of the cadet branch of the French Capetian dynasty. The historical ties between the Duchy of Brittany and this English earldom were maintained ceremonially by the Breton dukes even after England ceased to recognize the Breton dukes as earls of England and those dukes rendered homage to the King of France, rather than the English crown. It was then held either by members of the English royal families of Plantagenet and Tudor, or English nobles closely associated with the English crown. It was eventually merged into the English crown during the reign of Henry VII of England and has been recreated as a Dukedom.
Conan I nicknamed Le Tort was the Duke of Brittany from 990 to his death.
The counts of Nantes were originally the Frankish rulers of the Nantais under the Carolingians and eventually a capital city of the Duchy of Brittany. Their county served as a march against the Bretons of the Vannetais. Carolingian rulers would sometimes attack Brittany through the region of the Vannetais, making Nantes a strategic asset. In the mid-ninth century, the county finally fell to the Bretons and the title became a subsidiary title of the Breton rulers. The control of the title by the Breton dukes figured prominently in the history of the duchy. The County of Nantes was given to Hoel, a disinherited son of a duke. He lost the countship due to a popular uprising. That uprising presented an opportunity for King Henry II of England to attack the Breton duke. In the treaty ending their conflicts, the Breton duke awarded the county to Henry II.
The noble Breton family line of Porhoët is represented in modern times by the Franco-Breton House of Rohan.
The Viscounty or County of Léon was a feudal state in extreme western Brittany in the High Middle Ages. Though nominally a vassal of the sovereign duke of Brittany, Léon was functionally independent of any external controls until the viscounts came under attack by King Henry II of England. It thus became the focus of revolts and wars when Brittany was drawn into the Angevin empire.
Hawise of Rennes was sovereign Duchess of Brittany from 1066 until her death.
Bertha of Cornouaille, also known as Bertha of Brittany, was hereditary 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. She was the last member of the Breton House of Cornouaille to reign over Brittany.
Hoël I of Brittany was an illegitimate son of Alan II and Judith. He was Count of Nantes and Duke of Brittany from 960 to 981.
Judith of Nantes was titular Countess of Nantes from 1051 to her death in 1063.
