Niu Jin (pronunciation^ⓘ) (fl. 208–238) was a military general serving under the warlordCao Cao during the lateEastern Han dynasty of China. He continued serving in the state ofCao Wei, founded by Cao Cao's successorCao Pi, during theThree Kingdoms period of China.

Niu Jin participated in theBattle of Jiangling of 208, during which he volunteered to lead 300 horsemen to attack the enemy, but was only saved byCao Ren when he got surrounded.

Years later, he participated in the counter-attack against the invadingShu forces in 231 and scored a victory overZhuge Liang's unit, and pursued him to Mount Qi. In 234, he soundly defeated the Shu generalMa Dai on the battlefield and killed thousands of enemies. In 238, he followedSima Yi on hiscampaign against Gongsun Yuan and was promoted to General of the Rear (後將軍).

However, Niu Jin's accomplishments in his later years had only earned him the apprehension from the Simas, thus he was ordered to commit suicide by drinking poison. The exact reasons for his death as well as the year he died remain disputed. TheYuan Shi Juan states that the incident happened "after the Year of the Horse^[1]" and that Niu Jin was poisoned by drinking toxic wine. Other records state that it was because Niu Jin committed adultery with one of the Sima relatives and was assassinated with poison arrows "during the Year of the Cow".^[2] According to the rumor which accounted by several history records, an illegitimate child born in the Sima family wad actually the biological son of Niu Jin. The product of the affair between Niu Jin and the anonymous wife of Sima family member was the futureEmperor Yuan of Jin.^[3] Other historical records that mentioned this affairs washè lín yù lù, an anecdotal novel written byLuo Dajing duringSong dynasty;^[4]rong zhai sui bi, written by Hong Mai during Southern Song dynasty;^[5] andbin tui lu, unofficial historical notes written by Zhao Shanzheng duringMing dynasty.^[6]

A story from unknown origin also states that Niu Jin was killed since he was actually a distant relative of the former emperor; his death date and the accuracy of this statement are difficult to verify.

In the 14th-century historical novelRomance of the Three Kingdoms, Niu Jin was one ofCao Ren's subordinates. He chasedGan Ning back to Yiling during thebattle of Jiangling, but was surrounded by reinforcements led byZhou Yu, and was ultimately defeated. Niu Jin then regrouped and planned a night attack on Zhou Yu's camp, but in the end he was once again beaten, suffering another great loss.

• Lists of people of the Three Kingdoms

• Chen, Shou (3rd century).Records of the Three Kingdoms (Sanguozhi).
• Pei, Songzhi (5th century).Annotated Records of the Three Kingdoms (Sanguozhi zhu).

• Generals under Cao Cao
• Cao Wei generals
• Chinese politicians who died by suicide
• Suicides in Cao Wei

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