Cieszyn [ˈt͡ɕɛʂɨn] (Czech: Těšín, German: Teschen) is a border-town and the seat of Cieszyn County, Silesian Voivodeship, southern Poland. It has 36,109 inhabitants (2004). Cieszyn lies on the Olza River, a tributary of the Oder river, opposite Český Těšín.
It is situated in the heart of the historical region of Cieszyn Silesia. Until the end of World War I in 1918 it was a seat of the Duchy of Teschen. In 1920 Cieszyn Silesia was divided between the two newly created states of Poland and Czechoslovakia, with the smaller western suburbs of Teschen becoming part of Czechoslovakia as a new town called Český Těšín. The larger part of the town joined Poland as Cieszyn.
The town combines both Polish and Austrian peculiarities in the style of its buildings. Because of several major fires and subsequent reconstructions (the last one in the late 18th century), the picturesque old town is sometimes called Little Vienna. The only relic of the ancient castle is a square tower, dating from the 12th century and 10th century romanesque chapel.