Gau Southern Hanover–Brunswick (German: Gau Südhannover–Braunschweig) was a regional district established in 1933 in Nazi Germany. Initially the gau was a territorial component of both the Free State of Prussia and the Free State of Brunswick from 1933 to 1935. However after the German constituent states were abolished in 1935, the gaus replaced them in their responsibilities. Gau Southern Hanover-Brunswick was dismantled after Germany's defeat in 1945. The territory after the war became part of Lower Saxony in West Germany.