Empress Wu.

During the Tang Dynasty, Emperor Taizong favored his concubine Wu Meiniang. She fell in love with the crown prince Li Zhi, and the emperor asked her to become a nun before he died, with the promise that Li Zhi would bring her back to the palace in three years. Wu returned as the Empress Dowager and eliminated her rivals. After Li Zhi's death, Wu continued to control politics, even deposing his successor, Li Zhe, and proclaimed herself as the first female emperor, changing the name of the dynasty to Zhou. With the help of loyal ministers, Li Zhe was eventually reinstated, and the Tang dynasty was restored.