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). Its last mayor was Jan Prokopek Jensen, a member of the Social Democrats (Socialdemokraterne) political party.
The former Nordborg municipality was created in 1970 as the result of a kommunalreform ("Municipality Reform") that merged a number of existing parishes:
The town has been greatly influenced by the presence of Danfoss, a global producer of components for refrigeration and airconditioning, heating and motion control applications, headquartered in the town and founded in 1933. The presence of Danfoss has made the (now former) Nordborg municipality, over the years, the site of one of the largest industrial workplaces in Denmark.
In later years, the municipality saw the rise of another major industrial company, Linak, a global producer of electric linear actuator systems. Albeit much smaller than Danfoss (Linak global employment of approx. 1600 people compared to Danfoss 23,000 "Facts in Brief - Danfoss".), Linak is still a large local employer.
Within the town is Nordborg Castle, a historic castle whose premises are currently used as a boarding school.
On January 1, 2007 Nordborg municipality ceased to exist as the result of Kommunalreformen ("The Municipality Reform" of 2007). It was merged with Augustenborg, Broager, Gråsten, Sundeved, Sydals, and Sønderborg municipalities to form the new Sønderborg municipality. This created a municipality with an area of 499 km2 and a total population of 49,886 (2005).