King John I of Portugal reigned from 1385 to 1433 and was a significant figure in the history of Portugal. He was the founder of the Aviz dynasty and played a crucial role in establishing Portugal's independence from Castile after the decisive victory at the Battle of Aljubarrota in 1385. During his reign, John I promoted exploration and trade, which laid the groundwork for the Age of Discoveries. He was also known for his marriage to Philippa of Lancaster, which strengthened ties with England and produced several notable children, including Henry the Navigator, who would further advance Portuguese exploration.