John de Montfort was a notable figure in the 14th century, known for his role as the Duke of Brittany. Born around 1340, he was the son of John III, Duke of Brittany and Joan of Penthièvre. His life was marked by political intrigue and conflict, particularly during the Brittany Civil War. He became a key player in the struggle for control over Brittany, often opposing his half-brother, Charles de Blois. John de Montfort's efforts ultimately led to his recognition as Duke, and he played a significant role in the region's history until his death in 1399.