member of the Turkic subfamily (Turkic languages) of the Altaic language family, spoken in northeastern Siberia ( Sakha republic), in northeastern Russia. Because its speakers have been geographically isolated from other Turkic languages for centuries, Sakha has developed deviant features; it demonstrates closest affinity to the northeastern branch of Turkic languages.

Almost all the 360,000 ethnic Sakha (Yakut) speak the Sakha language as their mother tongue. Most also speak Russian. Sakha is sometimes used as a lingua franca among other northern peoples.