Liu Wu (劉悟) (died September 25, 825), formally the Prince of Pengcheng (彭城王), was a general of the Chinese Tang Dynasty, whose killing of his superior, the warlord Li Shidao, and subsequent submission to the imperial government, were the high point of Emperor Xianzong's campaign to end warlordism. During the subsequent reign of Emperor Muzong, however, Liu, angered by a conspiracy between an imperial eunuch and one of his subordinates, drifted away from the imperial government and ruled Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi) semi-independently.
It is not known when Liu Wu was born. His grandfather Liu Zhengchen (劉正臣) had served as the Tang military governor (Jiedushi) of Pinglu Circuit (平盧, then headquartered in modern Chaoyang, Liaoning) during the Anshi Rebellion and combatted the army of the rebel Yan, but was unable to capture the Yan northern capital Fanyang before being poisoned by his own subordinate Wang Xuanzhi (王玄志). During the time that Liu Wu's uncle Liu Quanliang (劉全諒) served as the military governor of Xuanwu Circuit (宣武, headquartered in modern Kaifeng, Henan), as he valued Liu Wu for Liu Wu's bravery and decisiveness, he made Liu Wu an officer under him, but Liu Wu subsequently committed a crime and fled to Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi), where the military governor of Zhaoyi, Wang Qianxiu (王虔休), made him an officer. Liu Wu soon became ill and resigned, and he went to the eastern capital Luoyang. Liu Quanliang had a storage of money at Luoyang, and Liu Wu broke into it and spent it. Liu Wu also associated with violent young men who killed people and dogs. As a result, Liu Wu was arrested and held at the jail of Henan Municipality (河南, i.e., the Luoyang region), but the defender of Luoyang Wei Xiaqing (韋夏卿) released him.