Jin Midi (134 BC – 29 September 86 BC, Chinese: 金日磾; pinyin: Jīn Mìdī, courtesy name Wengshu (翁叔), formally Marquess Jing of Du (秺敬侯)), was a Xiongnu Xiutu prince and a general of the Western Han dynasty. He was referred to as a non-Han "barbarian", either with the term Hu or Yidi. He was originally from the Xiutu Kingdom in central Gansu and served as co-regent early in the reign of the Emperor Zhao of Han. He was given the family name "Jin" ("Gold") by Emperor Wu of Han because he worshipped the golden statue of the Xiongnu which Huo Qubing captured in his military campaigns.

Jin Midi was born in 134 BC to a royal Xiongnu family. He was the heir of the Xiongnu's Prince of Xiutu, one of the major princes under the supreme ruler of the Xiongnu, the Junchen Chanyu. After Junchen's death in 126 BC, his brother Yizhixie succeeded him. During this time, the Prince of Xiutu and another major prince, the Prince of Hunye, were responsible for defending Xiongnu's southwestern border with Han dynasty in modern central and western Gansu.

In 121 BC, Emperor Wu of Han sent his general Huo Qubing to attack the Xiongnu, dealing a great defeat to the Xiongnu. In the campaign, Huo killed the Princes of Zhelan and Luhu, as well as 8,900 Xiongnu soldiers, while capturing the Prince of Hunye's son, chief assistant, and a number of officials, as well as golden statues that the Prince of Xiutu had forged to use to worship heaven. Yizhixie Chanyu was greatly displeased, and was considering summoning the Princes of Hunye and Xiutu to execute them. The princes, in fear, plotted to defect to Han. When Emperor Wu sent Huo to accept their surrender, the Prince of Xiutu changed his mind and tried to back out of defecting. The Prince of Hunye killed him and surrendered to Han, along with the region that he controlled.

Because the Prince of Xiutu was killed, Midi, as well as his mother the princess, as well as his brother Lun, were confiscated to serve as imperial servants. Midi was assigned to the imperial stables.

During an imperial feast, Emperor Wu ordered that horses be brought to him for him to examine. Midi, and a large number of fellow stable attendants, brought the horses, and as a number of Emperor Wu's beautiful concubines were in attendance, the attendants were struck by their beauty and were looking at them, but Midi did not dare to. Emperor Wu saw Midi and was impressed by his propriety, tall stature, and how healthy and strong the horses under Midi's care were. That same day, he awarded Midi robes and made him the director of the imperial stables, and thereafter became increasingly close to Midi. According to the Hanshu, the reaction of the court was not without some resentment:

Many of the emperor’s relatives and other persons in high position were secretly resentful, saying, ‘His Majesty [Emperor Wu] by some quirk of circumstance gets himself a barbarian boy (胡儿 hu’er) and what does he do but treat him with honor and respect!’ When the emperor heard of their remarks, he only treated Jin Midi more generously than ever.

— Han shu Chapter 68, translation by Watson (1974: 152-153).

As he remembered that the Prince of Xiutu had used golden statues to worship heaven, Emperor Wu gave Midi the surname Jin, meaning "gold". When Jin Midi's mother died, Emperor Wu had her portrait drawn and displayed at his later favorite palace, the Sweet Spring Palace, entitling the portrait, "The Princess of Xiutu" (i.e., not regarding her as a servant any more, but by her former status as princess). Two of Jin Midi's sons became close attendants to Emperor Wu and were favored by Emperor Wu. After one of the sons was grown, on one occasion, he was flirting with Emperor Wu's ladies in waiting when Jin Midi saw them. In anger at his son's inappropriate behavior, killed him, and then reported to Emperor Wu. Emperor Wu was greatly saddened but became even more impressed with Jin Midi.