Joanna of Castile
Queen of Castile from 1504 and of Aragon from 1516
Joanna of Castile (6 November 1479 – 12 April 1555), also known as Joanna the Mad, was a reigning queen of Castile and Aragon. She was the daughter of Isabella of Castile and Ferdinand II of Aragon. When her mother died in 1504, Joanna became Queen of Castile. However, her father ruled instead of her. When her father died in 1516, Joanna became Queen of Aragon, but her son Charles I reigned as king also.
Despite her titles, Joanna never really acted as queen. Her father had her locked in the royal palace. Later her son had her locked in a convent.