List of Spanish monarchs
This is a list of Spanish monarchs - that is, rulers of united Spain. The forerunners of the Spanish throne were the following:
Ferdinand II of Aragon and Isabella I of Castile. Although their kingdoms continued to be separate, with their personal union they ruled them together as one dominion. Ferdinand also conquered the southern part of Navarre and annexed it to Spain. 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 his grandfather Ferdinand on the Aragonese throne when Ferdinand died in 1516; thereafter the thrones were united.