Niu Sengru (牛僧孺), courtesy name Si'an (思黯), formally Duke Wenzhen of Qizhang (奇章文貞公), was a prominent statesman, scholar, chuanqi writer, and poet of China's Tang dynasty. Niu served multiple terms as a chancellor under Emperor Muzong and the latter's sons Emperor Jingzong and Emperor Wenzong. Alternately in and out of imperial favor and high office amid turbulence in the imperial court, Niu also served as the minister of war and a provincial military governor. Traditional historians often considered him a leader of the eponymous "Niu faction" in the Niu-Li factional struggles of the eighth-century Tang court, though contemporary scholars have questioned the degree to which Niu actively engaged in factional politics. Niu was regarded by contemporaries, including his political adversary Li Deyu, as an official of high integrity, and he was posthumously awarded prestigious honors after his death in the reign of Emperor Xuanzong.

Emperor Muzong of Tang, personal name Li Heng, né Li You (李宥), was an emperor of the Tang dynasty of China. He reigned from 820 to 824. Emperor Muzong was the son of Emperor Xianzong. He was created crown prince in 812 during the reign of Emperor Xianzong and, after Emperor Xianzong was allegedly assassinated by a eunuch, Li Heng was proclaimed emperor in 820.