Li Deyu (Chinese: 李德裕; pinyin: Lǐ Déyù; 787 – January 26, 850), courtesy name Wenrao (文饒), formally the Duke of Wei (衛公), was a Chinese poet, politician, and writer during the Tang Dynasty, serving as a chancellor during the reigns of brothers Emperor Wenzong and Emperor Wuzong and (briefly) their uncle Emperor Xuānzong. He was the leader of the so-called Li Faction in the decades-long Niu-Li Factional Struggles, and was particularly powerful during Emperor Wuzong's reign, dominating the court scene and guiding policies during the campaigns against the crumbling Huigu Khanate and against the warlord Liu Zhen. After Emperor Wuzong's death, Emperor Xuānzong, who had long despised him for his hold on power, had him demoted and banished, where he died in exile.