Zheng Zhong (traditional Chinese: 鄭眾; simplified Chinese: 郑众; pinyin: Zhèng Zhòng), courtesy name Jichan (季產) or Jiping (季平) (died 114), was the first Han dynasty eunuch with real power in government, thanks to the trust that Emperor He had in him for his contributions in overthrowing the clan of Empress Dowager Dou, particularly her autocratic brother Dou Xian. He was also a close associate of Emperor He's wife Empress Deng Sui and continued to be dominant after Emperor He's death, during her regency over his son Emperor Shang and Emperor An. He was also the first Eastern Han dynasty eunuch to be created a marquess. (The only Western Han dynasty eunuch who was created a marquess was Empress Xu Pingjun's father Xu Guanghan (許廣漢), whose creation was thanks to his relationship with his daughter and his son-in-law Emperor Xuan, not his post as a eunuch.)
Zheng was from Nanyang Commandery (roughly modern Nanyang, Henan) – the same commandery that the Eastern Han imperial clan dominated. He was described to be cautious, agile, and a deep thinker. He first served in the household of Liu Da, later Emperor Zhang, while he was still the crown prince under his father Emperor Ming. After Emperor Zhang ascended the throne in 75, Zheng Zhong was appointed as an Attendant at the Yellow Gates,. He was eventually promoted to the post of an imperial attendant (中常侍), and in the early reign of Emperor He (ca.90), he was made Prefect of the Palace Gardens.