Marie of Blois was a daughter of Joanna, Duchess of Brittany and Charles, Duke of Brittany.
Marie married Louis I, son of John II of France, in 1360.
Through marriage to Louis I, Duke of Anjou, she became Duchess of Anjou, Count of Maine, Duchess of Touraine, titular Queen of Naples and Jerusalem and Countess of Provence. Marie pawned her valuables and raised an army. In 1387 Louis II was formally recognized as Count in Aix-en-Provence.
In 1390, Louis, supported by the pope and the French, set sail for Naples.
Marie negotiated for a marriage between Louis and Yolande of Aragon, to prevent the Aragonese from obstructing him there. They finally wed in 1400.
Marie was an able administrator and on her deathbed revealed to Louis that she had saved the amount of 200,000 écus. This to make sure that she would be able to pay his ransom in case he would be captured.
With Louis I she had the following children:
Marie (1370 – after 1383)
Louis II of Anjou (1377 – 1417)
Charles (1380 – 1404, Angers), Prince of Taranto, Count of Roucy, Étampes, and Gien.