Jean I of Brittany was a notable historical figure who became the Duke of Brittany in 1341. Born in 1324, he was the son of John III, Duke of Brittany and Beatrice of England. His ascension to the dukedom was marked by a power struggle, as rival factions vied for control, leading to the Breton War of Succession. Despite his young age, Jean I was declared duke at just 16 years old. His reign was characterized by political instability and conflict, particularly with the Kingdom of France. Jean I's rule ended with his death in 1399, after which Brittany continued to navigate its complex political landscape.