The area has been populated by Slavic peoples since at least the 7th century.
According to legend, in 810 three sons of a prince – Bolko, Leszko and Cieszko, met here after a long pilgrimage, found a spring, and decided to found a new settlement.
They called it Cieszyn, from the words cieszym się ("I'm happy").
This well can be found at ulica Trzech Braci ("Three Brothers Street"), just west of the town square.

The town was the capital of the Duchy of Teschen since 1290, which was ruled by Piast dynasty until 1653 and by the Habsburg Dynasty of Austria until 1918.
It was in Teschen that Maria Theresa and Frederick II on in May 1779 signed the Teschen Peace Treaty, which put an end to the War of the Bavarian Succession.
In the 19th century Teschen was known for its ethnic, religious and cultural diversity, containing mostly German, Polish, Jewish and Czech communities.
There was also a small Hungarian community in the town consisting mostly of officers and clerks.

The town was divided in July 1920, by the Spa Conference, a body formed by the Versailles Treaty, leaving a Polish minority on the Czechoslovak side.
Its smaller western suburbs became what is now the town of Český Těšín in the Czech Republic.
During the interwar period two villages were merged into Cieszyn: Błogocice in 1923 and Bobrek in 1932.
After 1920 many ethnic Germans left the town, while many Poles from the Czechoslovakian part of the region moved in.
According to the Polish census of 1921, Cieszyn had 15,268 inhabitants, of whom 9,241 (60.5%) were Poles, 4,777 (31.2%) were Germans, 1014 (6.6%) were Jews, and 195 (1.3%) were Czechs.
The census from 1931 indicated 14,707 inhabitants, of whom 12,145 (82.7%) were Poles, while the rest consisted mostly of Germans and Jews (in 1937 estimated to be 12 and 8% respectively).

Cieszyn and Český Těšín were merged again in October 1938 when Poland annexed the Zaolzie area together with Český Těšín.
In 1939 Cieszyn Silesia was occupied by German forces and during World War II it was part of Nazi Germany.
Almost the entire Jewish community was murdered by the Nazis.

After World War II, the border between Poland and Czechoslovakia was restored to that of 1920.
Most Germans fled or were expelled and were replaced with Poles expelled from the Polish areas annexed by the Soviet Union.
Signs of the former German presence in the town were removed by a special committee.

On 19 July 1970, five firefighters from Cieszyn died when a bridge they were on fell into the Olza River, due to heavy flooding.
In 1977, Boguszowice, Gułdowy, Kalembice, Krasna, Mnisztwo, Pastwiska were amalgamated with Cieszyn and Marklowice.
The area has been populated by Slavic peoples since at least the 7th century. According to legend, in 810 three sons of a prince – Bolko, Leszko and Cieszko, met here after a long pilgrimage, found a spring, and decided to found a new settlement. They called it Cieszyn, from the words cieszym się ("I'm happy"). This well can be found at ulica Trzech Braci ("Three Brothers Street"), just west of the town square.
The town was the capital of the Duchy of Teschen since 1290, which was ruled by Piast dynasty until 1653 and by the Habsburg Dynasty of Austria until 1918. It was in Teschen that Maria Theresa and Frederick II on in May 1779 signed the Teschen Peace Treaty, which put an end to the War of the Bavarian Succession. In the 19th century Teschen was known for its ethnic, religious and cultural diversity, containing mostly German, Polish, Jewish and Czech communities. There was also a small Hungarian community in the town consisting mostly of officers and clerks.
The town was divided in July 1920, by the Spa Conference, a body formed by the Versailles Treaty, leaving a Polish minority on the Czechoslovak side. Its smaller western suburbs became what is now the town of Český Těšín in the Czech Republic. During the interwar period two villages were merged into Cieszyn: Błogocice in 1923 and Bobrek in 1932. After 1920 many ethnic Germans left the town, while many Poles from the Czechoslovakian part of the region moved in. According to the Polish census of 1921, Cieszyn had 15,268 inhabitants, of whom 9,241 (60.5%) were Poles, 4,777 (31.2%) were Germans, 1014 (6.6%) were Jews, and 195 (1.3%) were Czechs. The census from 1931 indicated 14,707 inhabitants, of whom 12,145 (82.7%) were Poles, while the rest consisted mostly of Germans and Jews (in 1937 estimated to be 12 and 8% respectively).
Cieszyn and Český Těšín were merged again in October 1938 when Poland annexed the Zaolzie area together with Český Těšín. In 1939 Cieszyn Silesia was occupied by German forces and during World War II it was part of Nazi Germany. Almost the entire Jewish community was murdered by the Nazis. 
After World War II, the border between Poland and Czechoslovakia was restored to that of 1920. Most Germans fled or were expelled and were replaced with Poles expelled from the Polish areas annexed by the Soviet Union. Signs of the former German presence in the town were removed by a special committee.
On 19 July 1970, five firefighters from Cieszyn died when a bridge they were on fell into the Olza River, due to heavy flooding. In 1977, Boguszowice, Gułdowy, Kalembice, Krasna, Mnisztwo, Pastwiska were amalgamated with Cieszyn and Marklowice.
Cieszyn