Zheng Tan (鄭覃) (died 842[1]), formally the Duke of Yingyang (滎陽公), was a Chinese historian and politician during the Tang dynasty, serving as a chancellor during the reign of Emperor Wenzong.
[2] As a result of his father's status, Zheng Tan was able to start his official career as a copyeditor (校書郎, Xiaoshu Lang) at Hongwen Institute (弘文館).
On an occasion when Emperor Xianzong wanted to make five eunuchs directors of troop food supplies for the northwestern border (with Huigu and Tufan), Zheng submitted a petition against the action, and the order was cancelled.
Zheng Tan, his colleague Cui Yan (崔郾), and three other advisory officials took the opportunity to advise him that he was spending too much time in feast and games, and was overly exhausting the imperial treasury with his rewards to his favorites.
Nevertheless, the soldiers were not allowing him to depart and head for his new post as the military governor of Yicheng Circuit (義成, headquartered in modern Anyang, Henan).
Wang Chengyuan requested Emperor Muzong to send a senior official to encourage the soldiers to obey the imperial order, so Emperor Muzong sent Zheng to Chengde, assisted by Wang Fan (王璠), to declare the imperial orders and to give a large cash award to the Chengde soldiers.
Meanwhile, Li Zongmin's junior colleague at the legislative bureau, Yang Rushi (楊汝士) and the deputy minister of rites (禮部侍郎, Libu Shilang) Qian Hui (錢徽) were in charge of overseeing the imperial examinations.
The military governor Duan Wenchang (a former chancellor) and the imperial scholar Li Shen both made secret pleas to Qian for certain examinees.
However, when the results were announced, the examinees that Duan and Li Shen recommended were not given passing results, while among those passing the examinations were Zheng Tan's brother Zheng Lang; Pei Zhuan (裴譔) the son of the military governor Pei Du (a former chancellor); Li Zongmin's son-in-law Su Chao (蘇巢); and Yang Rushi's brother Yang Yinshi (楊殷士).
This thus brought a popular uproar, and Duan submitted a report accusing Yang Rushi and Qian of being unfair.
He thus recommended Zheng to be the minister of public works (工部尚書, Gongbu Shangshu) but had him stripped of his assistant imperial scholar status.
[3] In 833, after Li Deyu became chancellor to replace Niu, there was a time when Emperor Wenzong complimented the knowledge that Yin You (殷侑) had about the classics, comparing him to Zheng.
Soon thereafter, without further consulting Li Zongmin, Emperor Wenzong made Zheng the chief imperial censor (御史大夫, Yushi Daifu).
Soon thereafter, Li Zongmin was sent out of the capital to serve as the military governor of Shannan West Circuit (山南西道, headquartered in modern Hanzhong, Shaanxi).
In summer 835, after Li Zongmin and his ally Yang Yuqing (楊虞卿) offended Emperor Wenzong and were exiled, Zheng was made the minister of justice (刑部尚書, Xingbu Shangshu).
In winter 835, he was made You Pushe (右僕射), one of the heads of the executive bureau (尚書省, Shangshu Sheng) as well as the principal of the imperial university (國子祭酒, Guozi Jijiu).
Zheng Tan was subsequently made chancellor de facto with the designation Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事), along with Li Shi.
It was not until spring 836, when Liu Congjian the military governor of Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi), submitted harshly worded petitions protesting the innocence of Wang Ya and Jia Su and accusing Qiu of crimes, did Qiu and the other eunuchs began to cut back on their behavior and allow Emperor Wenzong, as well as Li Shi and Zheng, to exercise their authority.
[5] For example, when Yang advocated for Li Zongmin, who was then forced to serve in the lowly post of military advisor to the prefect of Hengzhou (modern Hengyang in Hunan), to be promoted closer to the capital, Emperor Wenzong agreed, but Zheng opposed vehemently, stating as far that he would resign his chancellorship if Li Zongmin were promoted, leading to a heated argument between Yang and Zheng in Emperor Wenzong's presence.
(In the aftermaths of the argument, Li Zongmin was made the prefect of Hang Prefecture (杭州, in modern Hangzhou, Zhejiang).)
Li Jue, offended, responded, "Chen Yixing is obviously suspecting that there are chancellors who are stealing power from Your Imperial Majesty.