The Spanish Inquisition was established in 1478. It was authorized by Pope Sixtus IV at the request of Ferdinand II of Aragon and Isabella I of Castile, later known as the Catholic Monarchs.
The new institution differed from earlier medieval inquisitions because it operated closely under royal authority. Its initial purpose was to investigate whether converts to Catholicism—especially Jewish converts known as conversos—were secretly continuing to practice their former faith. It later expanded its attention to Muslim converts, Protestants, alleged heresy, censorship, and other offenses against religious orthodoxy.
The date 1478 refers to the papal authorization and formal establishment of the institution. The first inquisitors were not appointed until 1480, and the first major tribunal activity began in Seville in 1481. These later dates sometimes cause confusion in trivia questions, but 1478 is the standard founding year.
The Spanish Inquisition continued for centuries and was finally abolished in 1834. It became one of the most powerful and feared institutions of the Spanish monarchy, though its activities and death toll remain subjects of historical debate.