Joanna (Joanna the Mad), 1479?1555, Spanish queen of Castile and Len (1504?55), daughter of Ferdinand II and Isabella I. She succeeded to Castile and Len at the death of her mother. Ferdinand II briefly assumed the regency until he was replaced by Joanna's ambitious husband, Philip I. After Philip's death (1506), Ferdinand again assumed the rule, for Joanna had by this time become quite insane. At Ferdinand's death (1516) Joanna's 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.

See T. Miller, The Castles and the Crown (1963).

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