Nùng is a Tai–Kadai language spoken mostly in Cao Bằng and Lạng Sơn provinces in Vietnam. It is also known as Bu-Nong, Highland Nung, Nong, Tai Nung, Tay, and Tày Nùng. Nung is the name given to the various Tai languages of northern Vietnam that are spoken by peoples classified as Nùng by the Vietnamese government.In the 1999 census, it had about 850,000 speakers.