João I was the King of Portugal from 1385 until his death in 1433. He was a member of the Aviz dynasty and came to power after the decisive Battle of Aljubarrota, which secured Portugal's independence from Castile. His reign is noted for the establishment of a strong monarchy and the beginning of Portugal's age of exploration. Under João I, Portugal expanded its overseas trade and established important alliances, including the Treaty of Windsor with England. He was also the father of Henry the Navigator, who played a crucial role in the early days of the Portuguese Age of Discoveries.