From 1507 to 1517, Francisco Jiménez de Cisneros was Grand Inquisitor for the kingdom of Castile.
Cisneros was a Franciscan cardinal, archbishop of Toledo, and powerful royal adviser. In 1507 he became Grand Inquisitor of Castile, while the Inquisition in the Crown of Aragon was administered separately. This distinction explains why Castile is the precise answer rather than the broader label “Spain.”
His tenure coincided with major political and religious changes. Cisneros served as regent of Castile twice, helped govern after the deaths of Philip the Handsome and Ferdinand II, and supported campaigns to enforce Catholic uniformity. He also sponsored educational and scholarly projects, including the Complutensian Polyglot Bible.
A common mix-up is Aragon, because the Spanish Inquisition operated in both crowns. In 1507, however, Aragon had its own Grand Inquisitor, Juan Enguera, while Cisneros headed the Castilian jurisdiction.