Margaret of Penthièvre was a noblewoman from the 14th century, born around 1340 in Brittany, France. She was the daughter of John IV, Duke of Brittany and Joan of Penthièvre. Margaret became known for her marriage to Charles of Blois, which linked her family to the powerful House of Blois. Margaret played a significant role in the Brittany War of Succession, a conflict over the duchy’s control. After her husband's death in 1364, she continued to support his claims and was involved in the political struggles of the time. Her life reflects the complexities of noble alliances and the impact of warfare on families in medieval France.