| Joanna of Flanders | |
|---|---|
 | |
| Duchess consort of Brittany | |
| Tenure | 30 April 1341–16 September 1345 |
| Born | c. 1295 |
| Died | September 1374 (aged 78–79) |
| Spouse | John of Montfort |
| Issue | |
| House | Dampierre |
| Father | Louis I, Count of Nevers |
| Mother | Joan, Countess of Rethel |
Joanna of Flanders (c. 1295 – September 1374) was Duchess of Brittany by her marriage to John of Montfort. Much of her life was taken up in defense of the rights of her husband and, later, son to the dukedom, which was challenged by the House of Blois during the War of the Breton Succession. Known for her fiery personality, Joanna led the Montfort's cause after her husband had been captured by Philip VI of France, and began the fight-back. There, she displayed considerable skill as a military leader and gained the respect of her people.
While Joanna did not invent the concept of women in warfare, she revolutionized the role of women in power. Joanna was able to rally the House of Montfort and functioned immaculately as a social, political, and military leader.
Shortly after taking refuge in England, she was confined to Tickhill Castle by order of King Edward III.
Joanna was highly praised by the chronicler Jean Froissart for her courage and energy. Because of her feats of leadership, historian David Hume described her as "the most extraordinary woman of the age".
Joanna of Flanders has often been overlooked by historians, who tend to credit her actions to the house of Montfort rather than Joanna herself.