Joan of Penthièvre or Joan "the Lame (French: Jeanne de Penthièvre, Jeanne "la Boiteuse; c. 1319 – 10 September 1384) reigned as Duchess of Brittany together with her husband, Charles of Blois, between 1341 and 1364. Her ducal claims were contested by the House of Montfort, which prevailed only after an extensive civil war, the War of the Breton Succession. After the war, Joan remained titular Duchess of Brittany to her death. She was Countess of Penthièvre in her own right throughout her life.