Tønder Municipality is a kommune in the Region of Southern Denmark on the Jutland peninsula in south Denmark. The municipality covers an …Tønder Municipality is a kommune in the Region of Southern Denmark on the Jutland peninsula in south Denmark. The municipality covers an area of 1,252 km², and has a total population of 36,651. Its mayor is Jørgen Popp Petersen, a member of the regional Schleswig Party.