Jia Nanfeng (257 – 13 May 300), nicknamed Shi (峕), was a Chinese empress consort. She was a daughter of Jia Chong and the first wife of Emperor Hui of the Jin dynasty and also a granddaughter of Jia Kui. She is commonly seen as a villainous figure in Chinese history, as the person who provoked the War of the Eight Princes, leading to the Wu Hu rebellions and the Jin Dynasty's loss of northern and central China. Between July 291 to May 300, she ruled the Jin empire from behind the scenes by dominating her developmentally disabled husband.

She was a female politician of the Western Jin Dynasty , historically grouped with Empress Lü and Wu Zetian as "Lü, Jia, and Wu". Jia Nanfeng was cruel and tyrannical by nature and personally killed several people. At the age of fifteen, she was married to Crown Prince Sima Zhong . In the second month of the eighth year of the Tai Shi era (272 CE), she was installed as Crown Princess at the age of sixteen; during this period, she reportedly used a sharp halberd to kill a fetus in the womb of a pregnant concubine. In the first year of the Yong Xi era (290 CE), Sima Zhong ascended the throne as Emperor Hui of Jin, and Jia Nanfeng was installed as Empress. Emperor Hui was inherently foolish and simple-minded from birth, and Yang Jun, Grand Tutor (taifu 太傅) and Area Commander-in-chief (da dudu 大都督), monopolized power, forming cliques, attacking dissenters, and appointing many relatives and partisans, which caused "resentment among the imperial house and indignation throughout the land." Meanwhile, his daughter, Empress Dowager Yang Zhi, the widow of Emperor Wu of Jin, supported and assisted her father. To prevent Jia Nanfeng from interfering, her signature was required on every imperial decree and official document after Emperor Hui had signed it before they could take effect.

In the third month of the first year of the Yuan Kang era (291 CE), Jia Nanfeng launched a coup, executing the powerful minister Yang Jun. She also deposed Yang Zhi as a traitor, reduced her to the status of a commoner, and placed her under house arrest, ultimately causing her death through deprivation of food and proper care, as well as grief and severe mistreatment. From this point onward, control over the political situation was in her hands, although it was not yet entirely monopolized, and she still had to maintain the balance of power within the court. After this, government affairs were briefly controlled by Counsellor-in-chief (taizai, 太宰) Sima Liang (司馬亮, d. 291), the Prince of Runan 汝南, and Grand Guardian (taibao, 太保) Wei Guan (衛瓘, 220-291). Empress Jia herself supervised and intervened in the affairs of government and appointed several of her own relatives to high offices. However, dissatisfied with this arrangement and seeking more direct and greater power, Empress Jia forged an imperial decree ordering Sima Wei (司馬瑋 d. 291), the Prince of Chu, who held command over a unit of armed forces in the capital, to arrest both officials. This resulted in the deaths of Sima Liang and Wei Guan. In a subsequent purge, Sima Wei was accused of treason and executed. Jia Nanfeng then consolidated power, and subsequently "ruled the empire autocratically, commanding awe both domestically and abroad." During her administration, she implemented the Land Grant System, appointed Liu Song to establish the Nine Ranks System, and heavily employed Zhang Hua , who came from a humble background, and the virtuous minister Pei Wei to jointly assist in governance. She also suppressed rebellious minority tribes such as the Xiongnu, Di, and Qiang, leading to a period described as "tranquility at court and among the populace" and "peace across the land," historically known as the "Yuan Kang Era of Peace." However, on a personal level—which also severely damaged her political future and ultimately cost her life—she adopted increasingly unrestrained, arrogant, and capricious behavior. She attempted to falsely present her nephew, Jia Wu’s son Han Weizu, as her own child in order to depose Crown Prince Sima Yu. She also became notorious for engaging in numerous affairs with different men merely for variety, and for killing them afterward to keep them silent whenever possible. Even her allies Zhang, Pei, and Jia Mo—who were also her relatives—began plotting to remove her from power, though they eventually abandoned the plan. In the ninth year of Yuan Kang (299 CE), Jia Nanfeng falsely accused Crown Prince Sima Yu of treason and had him deposed. Sima Lun , Prince of Zhao, following a plan by Sun Xiu, incited Jia Nanfeng's faction to kill Crown Prince Sima Yu. Then, under the pretext of avenging the Crown Prince, he led troops into the palace, deposed Jia Nanfeng, imprisoned her in Jinyong City, and had her killed.

Jia Nanfeng governed for nine years during Emperor Hui's reign. She selected the capable and employed them without suspicion. During this period, the administration was considered commendable, society was relatively stable, and a rare period of peace emerged in the late Western Jin. However, Jia Nanfeng fell for the treacherous scheme of Sima Lun , Prince of Zhao, which led to the poisoning of Crown Prince Sima Yu, her own death, and Sima Lun's usurpation of the throne. Traditional historians often blamed her for the "War of the Eight Princes," while contemporary scholars generally believe the true instigator was the usurper Sima Lun, Prince of Zhao, and that Jia Nanfeng was essentially a victim of political struggle.

Jia Nanfeng was born in 257 to the Jin official Jia Chong and his second wife Guo Huai. She was their oldest daughter, although Jia Chong had two daughters from his previous marriage to noble lady Li Wan, a daughter of Li Feng. The couple had another daughter, Jia Wu (賈午), in 260. They also had two sons, both of whom died young. Jia Nanfeng also had a nursemaid, Xu Yi, who later served her as a trusted court maid.

In 271, Jia's father desperately wanted to avoid an assignment to guard the Guanzhong region and fend off attacks from Di and Qiang (氐羌) rebels, so he decided to have either Jia or her younger sister marry the developmentally disabled crown prince, Sima Zhong. The emperor initially rejected the idea, as he preferred Wei Guan's daughter as a bride for the crown prince. Indeed, Emperor Wu argued:

There are five reasons why Duke Wei's daughter is appropriate, and there are five reasons why Duke Jia's daughter is inappropriate. The Wei family are known for producing male children, and Lady Wei is mild-tempered, beautiful, tall, and fair-skinned. The Jia family lacks male children, and Lady Jia is jealous, ugly, short, and dark-skinned.

However, Guo Huai was on friendly terms with Empress Yang Yan, whose associates all greatly praised Jia's daughters. Eventually, Emperor Wu agreed, but selected Jia Wu to marry Crown Prince Zhong. When Wu was to wear formal dress to be examined, however, she was too young and too short for the dress, so Jia Nanfeng was chosen. They married on 2 April 272, and she was created crown princess. She was 15, and he was 13. She became quickly known for her jealousy, but she established a relationship with the crown prince where he both loved and feared her. For the rest of her life, she would have him firmly in her control. When several of his concubines became pregnant, she killed them herself in fits of jealousy; Emperor Wu was going to depose her, and only intercession by his second wife Empress Yang Zhi (Empress Yang Yan's cousin, whom he married after her death) led to Crown Princess Jia being spared. When, on one occasion, Wei hinted to Emperor Wu that Crown Prince Zhong was so unintelligent as to be an inappropriate heir, it was Crown Princess Jia who thought of the solution to Emperor Wu's subsequent inquiries of Crown Prince Zhong—having someone else write simple but correct answers to the inquiries, so that Emperor Wu was impressed.