Cheng Yuanzhen (程元振) (died 764?) was a Chinese eunuch, military general, and politician during the Tang dynasty. He was exceedingly powerful early in the reign of Emperor Daizong and was said to, in his attempts to consolidate his power, have killed or demoted a number of key generals and officials on his own whim, and thus drew the hatred from the other officials and generals. In 763, he was blamed for not warning Emperor Daizong about the Tubo invasion that eventually caused the capital Chang'an to fall to Tubo forces, forcing Emperor Daizong to flee. Emperor Daizong exiled him, and he died in exile.