The Small Fortress is a fortress forming a significant part of the town of Terezín in the Czech Republic. The former military fortress was established at the end of the 18th century together with the whole town of Terezín on the right bank of the Ohře River. It served as a prison in the 19th century and was also house of Imprisonment for Gavrilo Princip.

Terezín is a town in Litoměřice District in the Ústí nad Labem Region of the Czech Republic. It has about 2,800 inhabitants. It is a former military fortress composed of the citadel and adjacent walled garrison town. The town centre is well preserved and is protected by law as an urban monument reservation. Terezin is most infamously the location of the Nazis' notorious Theresienstadt Ghetto.