The North Auckland Peninsula, frequently referred to simply as the Northland Peninsula, is located in the far north of the North Island of New Zealand. The peninsula is easily confused with, though not the same as Northland Region, which occupies the top 80% of the peninsula. The remaining section of the peninsula is administratively part of the Auckland Region.
The exact length of the peninsula is difficult to ascertain, as it is possible to name several southerly extremities of it. The Northland Region begins at a narrowing of the peninsula close to the town of Wellsford, where the peninsula reaches a minimum width of just 15 kilometres.
There are two points further south, however, where the island's width is considerably narrower. These are both within the metropolitan area of the conurbation known as Auckland. In the west of the city, the Whau River, an estuarial arm of the Waitemata Harbour comes within two kilometres of the waters of the Manukau Harbour on the west coast. A few kilometres to the southeast is the Otahuhu isthmus. Here an arm of the Hauraki Gulf on the east coast comes just 1200 metres from the Manukau's waters. This would put the majority of Auckland city on the peninsula.
Although this third isthmus is perhaps the most logical point to consider as the start of the peninsula, few New Zealanders would agree that Auckland is on the North Auckland Peninsula, preferring to think of the whole area between the Otahuhu and Whau necks as The Auckland Isthmus.
If this is accepted, then the peninsula stretches northwest for 285 kilometres from the Whau, 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 are the Aupouri Peninsula - a peninsula on a peninsula - with the island narrowing to only some 10 kilometres in width for this final northern part of the island.
At its northern end, the Aupouri Peninsula reaches a number of capes each of which is claimed by some people to be the North Island's northernmost point: Cape Maria van Diemen, Cape Reinga, North Cape, and the Surville Cliffs. The honour actually goes to the latter of these, the cliffs being at a latitude of 34° 23' 47" South.
The North Auckland Peninsula features the massive gash of the Kaipara Harbour part way up its western (Tasman Sea) shore. This harbour is one of the largest natural harbours in the world, stretching some 65 kilometres in a north-south direction. Further north is a smaller natural harbour, the Hokianga, which is of historic and cultural significance within New Zealand, especially to the native Māori people. Another historically significant site on the North Auckland Peninsula is Waitangi and the surrounding Bay of Islands. This was a major settlement in early colonial New Zealand, and was the site of the Treaty of Waitangi, which is seen as the founding document of New Zealand's nationhood.
The largest settlement on the peninsula (other than parts of the Auckland conurbation) is Whangarei, on a natural harbour opening on the Pacific Ocean close to the peninsula's widest point.