Charles de Blois was a French nobleman born in 1319, known for his role in the Brittany War of Succession. He was the son of Guy de Blois and Margaret of Brittany, which positioned him as a key figure in the conflict over the duchy of Brittany. De Blois became the Duke of Brittany after marrying Joan of Penthièvre, who claimed the duchy. His reign was marked by battles against John of Montfort, his rival for the title. Charles de Blois was ultimately captured and killed in 1364, leading to the eventual victory of the Montfort faction.