Li Chengqi (Chinese: 李成器) (679 – January 5, 742), known as Wu Chengqi (Chinese: 武成器) during the reign of his grandmother Wu Zetian and as Li Xian (Chinese: 李憲) after 716, formally Emperor Rang (Chinese: 讓皇帝, literally, "the emperor who yielded"), was an imperial prince of the Chinese dynasty 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.
Read more about Li Chengqi: Background, During Emperor Zhongzong's and Emperor Ruizong's First Reigns, During Wu Zetian's Reign, During Emperor Zhongzong's Second Reign and Emperor Shang's Reign, During Emperor Ruizong's Second Reign, During Emperor Xuanzong's Reign, Ancestry