John III, nicknamed The Pious, was the King of Portugal and the Algarves from 1521 until his death in 1557. He was the son of King Manuel I and Maria of Aragon, the third daughter of King Ferdinand II of Aragon and Queen Isabella I of Castile. John succeeded his father in 1521 at the age of nineteen.

Manuel I, known as the Fortunate, was King of Portugal from 1495 to 1521. A member of the House of Aviz, Manuel was Duke of Beja and Viseu prior to succeeding his cousin, John II of Portugal, as monarch. Manuel ruled over a period of intensive expansion of the Portuguese Empire owing to the numerous Portuguese discoveries made during his reign. His sponsorship of Vasco da Gama led to the Portuguese discovery of the sea route to India in 1498, resulting in the creation of the Portuguese India Armadas, which guaranteed Portugal's monopoly on the spice trade. Manuel began the Portuguese colonization of the Americas and Portuguese India, and oversaw the establishment of a vast trade empire across Africa and Asia.