As the first queen in British history, the legitimacy of Mary I's kingship has been controversial since she succeeded to the throne. The first divorce of Henry VIII made Mary lose her legal status to inherit the throne. Edward VI's will designated Jane Gray as his successor. Although Mary executed Jane and became Queen with the support of Parliament, her marriage to Philip of Spain exacerbated people's doubts about the legitimacy of the rule. Political theories and thoughts since the late Middle Ages are also full of prejudice against women's rule. Mary I gradually established the legal status of female kingship by responding to the questions about the legitimacy of her kingship one by one. The legal establishment of female kingship laid the foundation for Elizabeth I's succession and accelerated the people's recognition of female monarchy.