Charles I, Duke of Brittany

Charles of Blois (1319 – 29 September 1364) claimed the title Duke of Brittany, from 1341 to his death.

Charles was born in Blois, the son of Guy I of Blois-Châtillon, count of Blois, by Margaret of Valois, a sister of king Philip VI of France. He was a devout man, who took piety to the extreme of mortifying his own flesh. It is said that he placed pebbles in his shoes, wore ropes tight with knots near his flesh and confessed every night in fear of sleeping in a state of sin. He was nevertheless an accomplished military leader, who inspired loyalty by his religious fervour.

On 4 June 1337 in Paris, he married Joanna of Dreux, heiress and niece of duke John III. Together, Charles and Joanna fought the House of Montfort in the Breton War of Succession (1341–1364), with the support of the crown of France. Despite his piety, Charles did not hesitate in ordering the massacre of 2000 civilians after the siege of Quimper. After initial successes, Charles was taken prisoner by the English in 1347. Thomas Dagworth was the official captor of Charles of Blois. He was released nine years afterwards against a ransom of about half a million ecús, and resumed the war against the Montforts.

Family
By his marriage to Joanna, he had five children:
 * John I of Blois-Châtillon (1340–1404) - also known as Jean de Blois
 * Guy
 * Henry (d. 1400)
 * Marie (1345–1404), Lady of Guise, married in 1360 Louis I of Naples
 * Marguerite, married in 1351 Charles de la Cerda (d. 1354)

Death and Legacy
Charles died in 1364 in the Battle of Auray which determined the end of the Breton War of Succession with the victory of the Montforts.

He was canonized as saint of the Roman Catholic church for his devotion to religion. However the canonization process was nullified by Pope Gregory XI at the request of Duke John V of Brittany, Charles' final opponent in the Breton War of Succession and the recognized Duke of Brittany under the first Treaty of Guerande.

Subsequently, in 1904, Charles was beatified and therefore may be referred to as the Blessed Charles of Blois. His Roman Catholic "Feast Day" is September 30.