Cieszyn Silesia or Tešín Silesia or Teschen Silesia (Polish: , Czech: or , German: Teschener Schlesien or Olsagebiet) is a historical region in south-eastern Silesia, centered on the towns of Cieszyn and Ceský Tešín 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 and has about 810,000 inhabitants, of which (44%) is in Poland, while (56%) is in the Czech Republic.