female emperor (of Japan)
Refers specifically to a woman who has ascended the Chrysanthemum Throne in her own right, as opposed to an empress consort.
Empress Suiko is considered Japan's first female emperor.
Debate continues over the enthronement of a female emperor.
Compound of 女性 (woman) and 天皇 (emperor). The term is modern, used in historical and political contexts to distinguish female sovereigns from male emperors.