The Di (Chinese: ; pinyin: Dī; Wade–Giles: Ti1; Old Chinese: *tˁij) were an ancient ethnic group that lived in western China, and are best known as one of the non-Han Chinese peoples that overran northern China during the Jin Dynasty (265–420) and the Sixteen Kingdoms period. This ethnic group should not be confused with the Dí 狄, which refers to unrelated nomadic peoples in northern China during the earlier Zhou Dynasty. The Di are thought to have been of proto-Tibetan origin, though there is a widespread belief among Chinese scholars that the Di have spoken an Altaic (specifically Turkic) language.
The Di lived in areas of the present-day provinces of Gansu, Qinghai, Sichuan and Shaanxi, and are culturally related to the Qiang. While the Qiang were herders who lived in the highlands, the Di farmed in the river valleys and lived in wood frame homes with mud walls. They might be related to the Geji (戈基) people in Qiang people stories. During the 4th and early 5th centuries, they established Former Qin and Later Liang states of that era's Sixteen Kingdoms. The Di were eventually assimilated into other populations. The modern Baima people living in southeast Gansu and northwest Sichuan may be descended from the Di.