The Boro–Garo languages are a branch of Sino-Tibetan languages, spoken primarily in Northeast India and parts of Bangladesh. The Boro–Garo languages form four groups: Boro, Garo, Koch and Deori. Boro–Garo languages were historically very widespread throughout the Brahmaputra Valley and in what are now the northern parts of Bangladesh, and it is speculated that the proto-Boro-Garo language was the lingua franca of the Brahmaputra valley before it was replaced by Assamese language, to which it has made major contributions.