Bolgar (also Bolğar), the language of the Bulgars, was a language, now extinct, whose classification is unknown. The established theory states that it was a Turkic language, but this theory is increasingly challenged by a theory linking Bolgar to the Iranian language group. It was used in Great Bulgaria, and later in Volga Bulgaria and in Danubian Bulgaria. The language became extinct in Danubian Bulgaria in the 9th century as the Bulgar nobility became gradually Slavonized through intermarriages with the Slavic majority there.

The language remained, however, in use by the population of Volga Bulgaria until the 13th or the 14th century when it adopted a number of words and constructions from the Kypchak language. The language spoken by the present-day Volga Tatars represents a mixture of Bolgar and Kypchak. The Chuvash group of the Volga Bolgars kept their language and it evolved into the modern Chuvash language.

The Old Tatar language also absorbed elements of the Bolgar language, because it appeared before the extinction of Bolgar.