Zhang Tang 張湯 (d. 115 BCE) was a high official of the mid-Former Han period 前漢 (206 BCE-8 CE).
He hailed from Duling 杜陵 (near modern Xi'an 西安, Shaanxi) and was an expert in penal and administrative law in his early years, when he was a minor official (li 吏) in the capital Chang'an 長安 and served Tian Sheng 田勝, Marquis of Zhouyang 周陽侯 and relative to Empress Dowager Wang 王太后. He later became 內史掾 and 茂陵尉.
During the counsellorship of Tian Fen 田蚡 he was appointed attendant censor (shiyushi 侍御史). In this office he was the main investigator of the sorcery case around Empress Chen 陳后 the process of which ended with the execution of more than 300 persons. Emperor Wu 漢武帝 (r. 141-87 BCE) thereupon promoted him to Superior grand master of the palace (taizhong dafu 太中大夫). Together with Zhao Yu 趙禹 he drafted a cruel penal law for the Han dynasty that ended the relaxed jurisdiction adhered to until that time.
He became Chamberlain for law enforcement (tingwei 廷尉) and was promoted to Censor-in-chief (yushi dafu 御史大夫) in 121 BCE. Zhang Tang suggested introducing a silver currency and a five-zhu coin for the unification of the currency system. He also supported the introduction of the state monopoly on the merchandise of salt and iron that was critically debated at the court. Zhang Tang likewise drafted the plan for the introduction of the taxation of merchants according to their cash in hand. He was later slandered by Counsellor-in-chief (chengxiang 丞相) Zhuang Qingdi 莊青翟 and his assistant Zhu Maichen 朱買臣 and forced to commit suicide.
Zhang Tang is credited with the authorship of a 27-chapters long law book called Yuegonglü 越宮律.