The Free State of Brunswick was a state of the German Reich in the time of the Weimar Republic. It was formed after the abolition of the Duchy of Brunswick in the course of the German Revolution of 1918–19. Its capital was Braunschweig (Brunswick). In 1933 it was de facto abolished by Nazi Germany. The free state was disestablished after the Second World War in 1946.

The Duchy of Brunswick was a historical German state. Its capital was the city of Brunswick . It was established as the successor state of the Principality of Brunswick-Wolfenbüttel by the Congress of Vienna in 1815. In the course of the 19th-century history of Germany, the duchy was part of the German Confederation, the North German Confederation and from 1871 the German Empire. It was disestablished after the end of World War I, its territory incorporated into the Weimar Republic as the Free State of Brunswick.