Qashan Duchy was a Bolghar Duchy in today Tatarstan. After th Mongol invasion to Bolghar in 13th century it became independent on Volga Bulgaria. It was a vassal of Golden Horde.
The capital was Qashan city. Population was agriculturists, citizens was craftsmen and tradesmen. In castles was found foundries for iron and copper, clay cooking utensils. In 1391 it was occupied by ushkuyniki, Russian river pirates, and finally in 1399 by Muscovy troops. In 1438-1440 it was reabsorbed to Khanate of Kazan and all Bolghar lands were united again.