In the late 15th century, Isabella of Castile (1451–1504) rose from princess to one of the most influential rulers of Europe. Her marriage to Ferdinand of Aragon united two powerful kingdoms, laying the foundation for modern Spain. Unlike many queens consort, Isabella was no passive figure—she ruled as an equal, sharing power in what was famously called the “joint monarchy.” Her reign was marked by bold decisions. In 1492, she and Ferdinand completed the Reconquista, capturing Granada and ending