The War of the Breton Succession (French: guerre de Succession de Bretagne, Breton: Brezel hrezh dugelezh Breizh) was a conflict between the Counts of Blois and the Montforts of Brittany for control of the Sovereign Duchy of Brittany, then a fief of the Kingdom of France. It was fought between 1341 and 12 April 1365. It is also known as the War of the Two Jeannes (French: guerre des deux Jeannes) due to the involvement of two queens of that name (Jeanne (Joanna) of Flanders and Jeanne de Penthivre).The war formed an integral part of the early Hundred Years' War due to the proxy involvement of the French and English governments in the conflict; the French supported the Blois (female heir) whilst the English backed the Montforts (male heir). The rival kings supported the Sovereign Duke of the principle opposite to their own claims to the French thronethe Plantagenet having claimed it by female succession, and the Valois by male succession. Montfort was ultimately successful following the Battle of Auray in 1364.

The Battle of Auray took place on 29 September 1364 at the Breton-French town of Auray. This battle was the decisive confrontation of the Breton War of Succession, a part of the Hundred Years' War.

In the battle, which began as a siege, a Breton army, led by Duke John de Montfort, assisted by English forces commanded by John Chandos, opposed a Breton army led by his rival Charles of Blois and assisted by French forces led by Bertrand du Guesclin.