The Columbia Encyclopedia, Sixth Edition. 2001-07.
Joanna, Spanish queen of Castile
(Joanna the Mad), 14791555, Spanish queen of Castile and León (150455), daughter of Ferdinand II and Isabella I. She succeeded to Castile and León at the death of her mother. Ferdinand II briefly assumed the regency until he was replaced by Joannas ambitious husband, Philip I. After Philips death (1506), Ferdinand again assumed the rule, for Joanna had by this time become quite insane. At Ferdinands death (1516) Joannas elder son, Charles (later Holy Roman Emperor Charles V), was proclaimed joint ruler of Castile with his mother. Joanna spent the rest of her life in the castle of Tordesillas. The pretense that she was not actually insane was sometimes used by the discontented, including Juan de Padilla, to justify revolts against the foreign ruler, Charles.