Isabella I, also called Isabella the Catholic, was Queen of Castile and León from 1474 until her death in 1504. She was also Queen of Aragon from 1479 until her death as the wife of King Ferdinand II. Reigning together over a dynastically unified Spain, Isabella and Ferdinand are known as the Catholic Monarchs.

Between 1492 and 1504, the Italian navigator and explorer Christopher Columbus led four transatlantic maritime expeditions in the name of the Catholic Monarchs of Spain to the Caribbean and to Central and South America. These voyages led to the widespread knowledge of the New World. This breakthrough inaugurated the period known as the Age of Discovery, which saw the colonization of the Americas, a related biological exchange, and trans-Atlantic trade. These events, the effects and consequences of which persist to the present, are often cited as the beginning of the modern era.