King John III of Portugal reigned from 1521 to 1557. He was the son of King Manuel I and Queen Maria of Portugal. His rule is noted for the expansion of the Portuguese Empire, particularly in India and Brazil. He also focused on strengthening the monarchy and promoting the arts and education. During his reign, John III faced challenges such as the Protestant Reformation and conflicts with Spain. He was a devout Catholic and supported the Inquisition in Portugal. His efforts in overseas exploration and trade helped solidify Portugal's position as a major maritime power during the Age of Discovery.