Who was the first queen of Spain?

The first queen of Spain is often considered to be Isabella I of Castile, who reigned from 1474 until her death in 1504. Alongside her husband, Ferdinand II of Aragon, she played a crucial role in the unification of Spain and the establishment of the Spanish monarchy. Their marriage in 1469 laid the foundation for the eventual political unification of the different kingdoms that would become modern Spain. Isabella is also known for sponsoring Christopher Columbus's 1492 voyage, which led to the discovery of the Americas.