Guan Gong, or Guan Di, is a Chinese god based on the historical Guan Yu, a third century military commander. He is often called the "Chinese God of War" though this title is not entirely appropriate.

The apotheosis of Guan Yu occurred in stages, as he was given ever large posthumous titles. Liu Shan, the son of Liu Bei, awarded Guan Yu the title of "Zhuangmiu Marquis" a few decades after his death. During the Ming dynasty he was credited with aiding Zhu Yuanzhang's fleet at the Battle of Boyang and later with repulsing the Japanese invasion of Korea by the Shogun Hideyoshi. The ruling Manchu house of the Qing dynasty associated with his martial qualities and awarded him ever larger titles, even exceeding that of the emperor himself. During the twentieth century Guan Yu was worshipped by the warlord Yuan Shikai, president and later emperor of China.

Today there are still numerous temples dedicated to Guan Yu, depicted with a red face and long beard, holding the Guan Dao, a sword with long handle (some rumored that it had been 80+ kilograms in weight, or about 170 pounds) which was named after him. He is also red-faced in Chinese operas.

In Hong Kong, a shrine for Guan Gong is located in each police station. Most Chinese policemen pay respect to him, and worship him. Members of the Triad worship him too.

People in jiang hu(江湖) respect him for he epitomise the Chinese concept of "Yi Qi" (義氣), which is a virtue these people seek among themselves.

In Hong Kong and among Cantonese speakers, he is often referred to as "Yi Gor" (二哥 second big brother) for he was second to Liu Bei in their blood brotherhood.