Li Xian () (29 January 655 – 13 March 684), courtesy name Mingyun (), formally Crown Prince Zhanghuai (), named Li De () from 675 to 680, was a crown prince of the Chinese Tang Dynasty. He was the sixth son of Emperor Gaozong, and the second son of his second wife Empress Wu (later known as Wu Zetian). He was known for writing commentaries for the Book of Later Han, the official history of the Eastern Han Dynasty. He became crown prince in 675 after his older brother Li Hong's death (which traditional historians believed to be a poisoning by Empress Wu), but soon fell out of favor and generosity with Empress Wu herself and that's what caused his downfall. In 680, Empress Wu had her associates accuse Li Xian of treason, and he was demoted to commoner rank and exiled. In 684, after Emperor Gaozong's death, Empress Wu, then empress dowager, had her associate Qiu Shenji (丘神勣) visit Li Xian to force him to commit suicide. In 706, his younger brother Emperor Zhongzong provided Li Xian with an honorable burial by interring his remains at the Qianling Mausoleum. Background Li Xian was born on 29 January 655, as the sixth son of Emperor Gaozong and the second son of his then-favorite concubine Consort Wu (later known as Wu Zetian). There were, however, persistent rumors inside the palace that he was not actually born of Consort Wu but of her older sister Wu Shun (who was later created the Lady of Han). In 655, the same year that his mother Consort Wu displaced Emperor Gaozong's first wife Empress Wang as empress, Li Xian was created the Prince of Lu. In 656, he was initially titularly given the post of prefect of Qi Prefecture (岐州, roughly modern Baoji, Shaanxi), and then the dual posts as prefect of the capital prefecture Yong Prefecture (雍州, roughly modern Xi'an, Shaanxi) and commandant at You Prefecture (幽州, roughly modern Beijing). It was said that his behavior was elegant, even in his youth, and, according to a comment that Emperor Gaozong made to the chancellor Li Ji, he had studied the Classic of History, Classic of Rites, Analects, and a number of ancient poems and could remember them clearly. In 661, his title was changed to Prince of Pei, and he was given the titles of commandant at Yang Prefecture (揚州, roughly modern Yangzhou, Jiangsu)