The Northland Peninsula, called the North Auckland Peninsula in earlier times, is in the far north of the North Island of New Zealand. It is joined to the rest of the island by the Auckland isthmus, a narrow piece of land between the Waitematā Harbour and the Manukau Harbour in the middle of the Auckland metropolitan area. The peninsula is not conterminous with the local government area of Northland Region, which occupies the northern 80% of the peninsula. The southern section of the peninsula is administratively part of the Auckland Region.
The peninsula stretches northwest for about 330 kilometres from the Auckland isthmus (or Tamaki isthmus), reaching a maximum width of 85 kilometres. It has a convoluted coastline, with many smaller peninsulas branching off it.
The last 100 kilometres of its length is the Aupouri Peninsula – a peninsula on a peninsula – narrowing to only some 10 kilometres in width. At its northern end, the Aupouri Peninsula includes a number of capes: Cape Maria van Diemen, Cape Reinga, North Cape, and the Surville Cliffs, the northernmost point, at latitude 34° 23' 47" South.
The Kaipara Harbour part way up the peninsula's western (Tasman Sea) shore is one of the largest harbours in the world, stretching some 65 kilometres from north to south. Further north is the smaller Hokianga harbour, which is of historic and cultural significance, especially to the Māori people. Another historically significant site is Waitangi and the surrounding Bay of Islands. This was a major settlement in early colonial New Zealand, and was the site of the first signing of the Treaty of Waitangi, which is seen as the founding document of New Zealand's nationhood.
- Stone, R. C. J. (2001). From Tamaki-Makau-Rau to Auckland. Auckland University Press. p. 1.
... the Tamaki isthmus .... This ... landbridge takes shape where the Northland peninsula ends ....
- Orange, Claudia (2 March 2009). "Northland region - Geography". Te Ara - the Encyclopedia of New Zealand. Retrieved 24 December 2012.
- Franklin, Samuel Harvey (1966). "North Auckland region". In A. H. McLintock (ed.). An Encyclopaedia of New Zealand. Retrieved 24 December 2012.