Isabella I, queen of Castile and León (b. 1451)
Isabella I (Spanish: Isabel I; 22 April 1451 – 26 November 1504) was Queen of Castile from 1474 until her death in 1504, reigning over a dynastically unified Spain together with her husband, King Ferdinand II of Aragon. She was Queen of Aragon after Ferdinand II ascended to that throne in 1479. Together, Isabella and Ferdinand are known as the Catholic Monarchs.After a struggle to claim the throne, Isabella reorganized the governmental system, brought the crime rate to the lowest it had been in years, and unburdened the kingdom of the enormous debt her half-brother King Henry IV had left behind. Isabella's marriage to Ferdinand in 1469 created the basis of the de facto unification of Spain. Her reforms and those she made with her husband had an influence that extended well beyond the borders of their united kingdoms.

Isabella I of Castile and Ferdinand II of Aragon are known for being the first monarchs to be referred to as "Queen of Spain" and "King of Spain" respectively, labeled such for completing the Reconquista, for issuing the Alhambra Decree which ordered the mass expulsion of Jews and Muslims from Spain, for establishing the Spanish Inquisition, for supporting and financing Christopher Columbus's 1492 voyage that led to the discovery of the New World by Europeans and established the Spanish empire, for making Spain a major power in Europe and much of the world, and for ushering in the Spanish Golden Age. Isabella was granted, together with her husband, the title of "Catholic monarch" by Pope Alexander VI, and was recognized in 1974 as a Servant of God by the Catholic Church.