Joanna of Castile
In 1506, Joanna's husband Philip became king of Castile ''jure uxoris'' as Philip I, initiating the rule of the Habsburgs in the Spanish kingdoms. Philip died that same year. Despite being the ruling queen of Castile, Joanna had little effect on national policy during her reign as she was declared insane and confined in the Royal Palace in Tordesillas under the orders of her father, who ruled as regent until his death in 1516, when she inherited his kingdom as well. Her son Charles I became king, and during his reign Joanna was nominally co-monarch but remained confined until her death. Joanna died aged 75 in 1555, at which point her son Charles, the Holy Roman Emperor, became the sole ruler of Castile and Aragon. Provided by Wikipedia