Bai is a Sino-Tibetan language spoken in China, primarily in Yunnan Province, by the Bai people. The language has over a million speakers and is divided into three or four main dialects. Bai syllables are always open, with a rich set of vowels and eight tones. The tones are divided into two groups with modal and non-modal phonation. There is a small amount of traditional literature written with Chinese characters, Bowen (僰文), as well as a number of recent publications printed with a recently standardized system of romanisation using the Latin alphabet.

Sino-Tibetan, also cited as Trans-Himalayan in a few sources, is a family of more than 400 languages, second only to Indo-European in number of native speakers. Around 1.4 billion people speak a Sino-Tibetan language. The vast majority of these are the 1.3 billion native speakers of Sinitic languages. Other Sino-Tibetan languages with large numbers of speakers include Burmese and the Tibetic languages. Other languages of the family are spoken in the Himalayas, the Southeast Asian Massif, and the eastern edge of the Tibetan Plateau. Most of these have small speech communities in remote mountain areas, and as such are poorly documented.