Chen Gong (died 198) was an advisor to the warlord Lü Bu during the late Han Dynasty period of Chinese history. However, he started his career under Cao Cao before defecting to Lü Bu and was executed when the latter was defeated by Cao.
In Luo Guanzhong's historical novel Romance of the Three Kingdoms, Chen Gong was given a positive makeover. He was said to have given up his official post to follow Cao Cao, who was then on the run after an attempted assassination on Dong Zhuo, a tyrannical warlord holding the emperor hostage in the imperial court. However, he left Cao Cao when he thought the latter was not an upright man either.
Read more about Chen Gong: Biography, In Fiction