Coordinates: 54°59′07″N 50°23′52″E / 54.9852722322°N 50.3977194544°E
Bilär (Tatar Cyrillic: Биләр; also Bilyar, Bülär, Бүләр) was a medieval city in Volga Bulgaria and its second capital before the Mongol invasion of Volga Bulgaria. It was located on the left bank of the Small Cheremshan River in modern-day Alexeyevsky District of the Republic of Tatarstan.
The city was founded by the indigenous Bilyar tribe of the Volga Bulgars. In the Rus chronicles, it was also known as "Great City" (Великий город), because its population reputedly was in excess of 100,000. Bilyar was one of the main trade centers in the Middle Volga, and alternatively with the Bulgar city and Nur-Suvar served as the capital of Volga Bulgaria in the 12th and 13th centuries. In 1236, the city was sacked by the army of Batu Khan. The city was later rebuilt, but it never regained its former size or power. The city's ruins (nearly 8 km²) were explored by Rychkov, Tatischev, Khalikov and Khuchin.
Near old Bilär in 1654 was founded a Russian border fort Bilyarsk. Today is an ethnic Russian village. In 1930-1963 Bilyarsk was an administrative center of Bilyar District. By the 2000 census, its population was 2,270. It is a birthplace of chemist Alexander Arbuzov.