According to legend, Cieszyn was established in 810 by the three brothers Leszko, Bolko and Cieszko in memory of their meeting after a long separation. Historians claim that Cieszyn was established at the end of the 10th century. The first written mention of the town dates from 1155, whereas the original founding of the town took place between 1217 and 1223. At the end of the 13th century, Cieszyn became the capital of the Duchy of Cieszyn, ruled by the Piast dynasty until the middle of the 17th century when it was taken over by the Habsburg dynasty.
In 1920, the town was divided into two parts, with the left-bank part becoming part of Czechoslovakia and so creating the town of Český Těsín. During World War II, the towns became one again, only to be parted once more in 1945 to return to their pre-war state. Together the towns constitute an important communication centre on the joint Czech-Polish-Slovakian borders (there are three Polish-Czech border crossings). As district towns, they constitute the educational, cultural and administration centre for the whole of Cieszyn Silesia, on both sides of the Olza River. Together they form the capital of the Cieszyn Silesia Euroregion.