Li Cong (李琮) (died 18 June 752[1]), né Li Sizhi (李嗣直), known as Li Tan (李潭) from 725 to 736, posthumously honored Crown Prince Jingde (靖德太子) and then Emperor Fengtian (奉天皇帝, literally, "the emperor who submitted to Heaven"), was an imperial prince of the Chinese Tang dynasty.
In 715, however, he was bypassed for the crown prince position when his younger brother Li Siqian the Prince of Ying was selected, as Li Siqian's mother Consort Zhao was then Emperor Xuanzong's favorite concubine.
In 716, Li Sizhi was made the Protectorate General to Pacify the West and received the title of "Comforter of the Non-Han of the Hedong [(modern Shanxi)], Guannei [(i.e., Guanzhong)], and Longyou [(modern eastern Gansu)] Regions" (安撫河東關內隴右諸蕃大使, Anfu Hedong Guannei Longyou Zhufan Dashi), although there was no evidence that he actually left the capital Chang'an.
In 727, Li Tan became the military governor (jiedushi) of Hexi Circuit (河西, modern central and western Gansu) as well as the commandant at Liang Prefecture (涼州, roughly modern Wuwei, Gansu), but, as was the case with 10 other brothers of his who received similar titles, did not actually take up the command.
The emperor was implying that someone with a disfigured face was not fit to rule, and this might be the reason why Li Cong was always bypassed and never became crown prince.