The Nùng are a Central Tai-speaking ethnic group living primarily in northeastern Vietnam and southwestern Guangxi. The Nùng sometimes call themselves Thổ, which literally means autochthonous. Their ethnonym is often mingled with that of the Tày as Tày-Nùng. According to the Vietnam census, the population of the Nùng numbered about 856,412 by 1999, 968,800 by 2009, and 1,083,298 by 2019. They are the third largest Tai-speaking group, preceded by the Tày and the Thái, and sixth overall among national minority groups.

The Tày people, also known as the Thổ, T'o, Tai Tho, Ngan, Phen, Thu Lao, or Pa Di, are a Central Tai-speaking ethnic group who live in northern Vietnam. According to a 2009 census, there are 1.7 million Tày people living in Vietnam. This makes them the second largest ethnic group in Vietnam after the majority Kinh (Vietnamese) ethnic group. Most live in northern Vietnam in the Cao Bằng, Lạng Sơn, Bắc Kạn, Thái Nguyên, and Quảng Ninh provinces, along the valleys and the lower slopes of the mountains. They also live in some regions of the Bắc Ninh and Bắc Giang provinces. They inhabit fertile plains and are generally agriculturalists, mainly cultivating rice. They also cultivate maize, and sweet potato among other things.