The Tsetsaut language is an extinct Athabascan language formerly spoken by the now-extinct Tsetsaut in the Portland Canal area of northwestern British Columbia. Virtually everything known of the language comes from the limited material recorded by Franz Boas in 1894 from two Tsetsaut slaves of the Nisga'a, which is enough to establish that Tsetsaut formed its own branch of Athabaskan. It is not known precisely when the language became extinct. One speaker was still alive in 1927.