John I of Brittany was a medieval duke who ruled from 1237 until his death in 1286. He was the son of Peter I, Duke of Brittany and Alix of Thouars. John I's reign was marked by his efforts to strengthen the duchy and maintain its independence from the influence of the French crown. During his rule, John I faced challenges, including conflicts with neighboring regions and internal disputes. He was known for his diplomatic skills and worked to secure alliances through marriage. His legacy includes the continued development of Brittany as a distinct political entity in France.