Nordborg (German: Norburg), is a town with a population of 6,191 (1 January 2014) and a former municipality (Danish, kommune) in Sønderborg Municipality, Region of Southern Denmark on the northwest half of the island of Als off the east coast of the Jutland peninsula in south Denmark. The former Nordborg municipality covered an area of 125 km², and had a total population of 13,956 (2005).