Li Chengqi () (679 – January 5, 742), known as Wu Chengqi () during the reign of his grandmother Wu Zetian and as Li Xian () after 716, formally Emperor Rang (, literally, "the emperor who yielded"), was an imperial prince of the Tang Dynasty who served as crown prince during the first reign of his father Emperor Ruizong, who yielded that position to his younger brother Li Longji (Emperor Xuanzong) during Emperor Ruizong's second reign. Li Chengqi had a number of children, including his oldest son, Li Jin (Tang Dynasty), the prince of Ruyang, who was called one of the Eight Immortals of the Wine Cup by famous poet Du Fu. According to historical records, Li Chengqi was close to his younger brother, Li Longji (later Emperor Xuanzong), and was never ambitious. Despite his never having been emperor, he was posthumously honored as an emperor by Emperor Xuanzong. Background Li Chengqi was born in 679, during the reign of his grandfather Emperor Gaozong. He was the oldest son of Li Dan, who was then the Prince of Yu, and Li Dan's wife Princess Liu. Sometime after his birth, he was created the Prince of Yongping. During Emperor Zhongzong's and Emperor Ruizong's first reigns Emperor Gaozong died in 683 and was succeeded by Li Chengqi's uncle Li Zhe the Crown Prince (as Emperor Zhongzong), but actual power was in the hands of Li Chengqi's grandmother Empress Wu (later known as Wu Zetian), as empress dowager and regent. In 684, after Emperor Zhongzong showed signs of independence, she deposed him and replaced him with Li Chengqi's father Li Dan (as Emperor Ruizong), but thereafter held onto power even more firmly. After Emperor Ruizong's ascension, Li Chengqi was created crown prince, and his mother Princess Liu was created empress. In 688, when Empress Dowager Wu held a grand ceremony to offer sacrifices to the god of the Luo River (洛水, which flowed near the eastern capital Luoyang), she had Emperor Ruizong and Li Chengqi offer sacrifices after her. She also had them offer sacrifices after her when she, in 689, offered sacrifices to the god of heaven, the past emperors of Tang Dynasty, her father Wu Shihuo (武士彠), and the gods of the five elements. During Wu Zetian's reign In 690, Empress Dowager Wu had Emperor Ruizong yield the throne to her, establishing a new Zhou Dynasty as Empress Regnant and interrupting