Zheng Ji 鄭吉 (d. 49 BCE) was an official of the late Former Han period 前漢 (206 BCE-8 CE).
He haield from Guiji 會稽 (modern Shaoxing 紹興, Jiangsu) and participated in several expeditions in the Western Territories 西域. During the reign of Emperor Zhao 漢昭帝 (r. 87-74 BCE) he was appointed attendant gentleman (shilang 侍郎) and organised the military colonies in Quli 渠黎. Zheng Ji was a commander when the state of Cheshi 車師 was finally brought into subordination and was therefore appointed commander of the guard (wei sima 衛司馬). In 69 BCE he took over command of the native troops from Quli and Qiuci 龜茲 that were sent out to welcome the Xiongnu 匈奴 khan Rizhu 日逐 who declared to be willing to submit to the Han empire. This event was the final act for the domination by the Han empire of the Western Territories. Zheng Ji was therefore given the title of Marquis of Anyuan 安遠侯 and was appointed Protector-general (duhu 都護) of the new protectorate, residing in Wulei 烏壘.
His posthumous title is Marquis Miao 繆侯.