Ferdinand II of Aragon (Fernando de Aragón in Spanish and Ferran d'Aragó in Catalan), nicknamed the Catholic (March 10, 1452 – June 23, 1516) was king of Aragon, Castile, Sicily, Naples and Navarre and Count of Barcelona. This monarch is also known as Fernando el Católico and Ferran el Catòlic.

He became Ferdinand V of Castile when he married Isabella I of Castile. They united their two kingdoms, running them as one country though they remained officially separate. He was also the king of Sicily (as Ferdinand II) from 1468 to 1516 and Naples (as Ferdinand III) from 1504 to 1516.

Their children included Joanna of Castile and Catherine of Aragon. Because of the power of their joint kingdoms, their daughters married with several European dynasties, setting the bases for the huge heritage of her grandson Charles V.

In November 1511 Ferdinand and Henry VIII of England signed the Treaty of Westminster, pledging mutual aid between the two against France. Earlier that year, Ferdinand had conquered the southern half of the Kingdom of Navarre and annexed it to Spain. Since he was a widower by then, he married the much younger Germaine of Foix (1490-1538), a grand-daughter of Queen Leonor of Navarre.

After Isabella left her kingdom to her daughter Joanna, Ferdinand served as her regent during her insanity. Though rebuffed by the Castilian nobility and replaced with Joanna's husband Philip I of Castile, he resumed the regency after Philip's death in 1506. Joanna's son, the Holy Roman Emperor Charles V, succeeded her on the throne of Castile and he also succeeded on the throne of Aragon when Ferdinand died in 1516. Thereafter the two thrones were united; see List of Spanish monarchs.

Some authors think that he was the inspiration for Niccolò Machiavelli's The Prince, but others do not.

See also

• Spanish Inquisition
• Monarchs of Naples and Sicily
• Cardinal Cisneros