Isabella of France

The She-Wolf of France: daughter of Philip IV, married at twelve to Edward II of England as part of a settlement of Anglo-French disputes. After enduring her husband's lavish favoritism of Piers Gaveston and Hugh Despenser, she returned to France, took Roger Mortimer as her lover, and led an invasion that deposed her husband in 1327. Her son Edward III's claim to the French throne — through her, after her brothers all died sonless — was the legal pretext for the Hundred Years' War.