Cieszyn Silesia, Těšín Silesia or Teschen Silesia is a historical region in south-eastern Silesia, centered on the towns of Cieszyn and Český Těšín and bisected by the Olza River. Since 1920 it has been divided between Poland and Czechoslovakia, and later the Czech Republic. It covers an area of about 2,280 square kilometres (880 sq mi) and has about 810,000 inhabitants, of which 1,002 square kilometres (387 sq mi) (44%) is in Poland, while 1,280 square kilometres (494 sq mi) (56%) is in the Czech Republic.

Cieszyn is a border town in southern Poland on the east bank of the Olza River, and the administrative seat of Cieszyn County, Silesian Voivodeship. The town has 33,500 inhabitants, and lies opposite Český Těšín in the Czech Republic. Both towns belong to the historical region of Cieszyn Silesia, and formerly constituted the capital of the Duchy of Cieszyn as a single town.