Cheng Yin was a general controlling parts of Guanzhong during the late Han Dynasty period of Chinese history. He was born in Hedong prefecture (河東) of Sili commandery (司隷). When Cao Cao invaded Guanzhong, Cheng Yin joined a coalition resisting Cao Cao with Ma Chao, Han Sui, etc. However, the coalition was defeated in the Battle of Tong Pass and he fled to seek refuge under Zhang Lu in Hanzhong. When Zhang Lu surrendered to Cao Cao, Cheng Yin followed.
In Luo Guanzhong's historical novel Romance of the Three Kingdoms, Cheng was one of the eight generals serving under Han Sui. He assaulted Chang'an and guarded it from Cao Cao, but was killed when Cao Cao retook the city.