Ferdinand II of Aragon

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 II) from 1468 to 1516 and Naples (as III) from 1504 to 1516.

Ferdinand also conquered the southern half of Navarre and annexed it to Spain. Since he was a widower by then, he married Germana of Foix[?].

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 his regency after Philip's death. Joanna's son, the Holy Roman Emperor Charles V, succeeded her on the throne of Castile; and he also succeeded Ferdinand on the Aragonese throne when Ferdinand died in 1516. Thereafter the thrones were united; see List of Spanish monarchs.

Some authors think that he was the inspiration for Niccolo Machiavelli's The Prince.

See also: Spanish Inquisition, Monarchs of Naples and Sicily.