Guan Yu ([kwán ỳ] (listen); died January or February 220), courtesy name Yunchang, was a military general serving under the warlord Liu Bei during the late Eastern Han dynasty of China. Along with Zhang Fei, he shared a brotherly relationship with Liu Bei and accompanied him on most of his early exploits. Guan Yu played a significant role in the events leading up to the end of the Han dynasty and the establishment of Liu Bei's state of Shu Han during the Three Kingdoms period. While he is remembered for his loyalty towards Liu Bei, he is also known for repaying Cao Cao's kindness by slaying Yan Liang, a general under Cao Cao's rival Yuan Shao, at the Battle of Boma. After Liu Bei gained control of Yi Province in 214, Guan Yu remained in Jing Province to govern and defend the area for about seven years. In 219, while he was away fighting Cao Cao's forces at the Battle of Fancheng, Liu Bei's ally Sun Quan broke the Sun–Liu alliance and sent his general Lü Meng to conquer Liu Bei's territories in Jing Province. By the time Guan Yu found out about the loss of Jing Province after his defeat at Fancheng, it was too late. He was subsequently captured in an ambush by Sun Quan's forces and executed.
Guan Yu's life was lionised and his achievements glorified to such an extent after his death that he was deified during the Sui dynasty. Through generations of story telling, culminating in the 14th-century historical novel Romance of the Three Kingdoms, his deeds and moral qualities have been given immense emphasis, making Guan Yu one of East Asia's most popular paradigms of loyalty and righteousness. He is still worshipped by many Chinese people today. In religious devotion he is reverentially called the "Emperor Guan" (Guān Dì) or "Lord Guan" (Guān Gōng). He is a deity worshipped in Chinese folk religion, popular Confucianism, Taoism, and Chinese Buddhism, and small shrines to him are almost ubiquitous in traditional Chinese shops and restaurants. His hometown Yuncheng has also named its airport after him.