The Auckland Region is one of the sixteen regions of New Zealand, named for the city of Auckland, the country's largest urban area. The region encompasses the Auckland metropolitan area, smaller towns, rural areas, and the islands of the Hauraki Gulf. With one third of the nation's residents, it has by far the biggest population and economy of any region of New Zealand, but the second-smallest land area.
On 1 November 2010, the Auckland Region became a unitary authority controlled by the Auckland Council, replacing the previous regional council and seven local councils. In the process, an area in its southeastern corner was transferred to the neighbouring Waikato Region. The name "Auckland Region" remains present in casual usage.
On the mainland, the region extends from the mouth of the Kaipara Harbour in the north across the southern stretches of the North Auckland Peninsula, past the Waitakere Ranges and the isthmus of Auckland and across the low-lying land surrounding the Manukau Harbour. The region ends within a few kilometres of the mouth of the Waikato River. It is bordered in the north by the Northland Region, and in the south by the Waikato Region. It also includes the islands of the Hauraki Gulf.
The Hunua Ranges and the adjacent coastline along the Firth of Thames were part of the region until the Auckland Council was formed in late 2010, when they were transferred to the neighbouring Waikato Region. In land area it is smaller than all the other regions and unitary authorities except Nelson. Its highest point is the summit of Little Barrier Island, at 722 metres.
The Auckland Region is built on a basement of greywacke rocks that form many of the islands in the Hauraki Gulf, the Hunua Ranges, and land south of Port Waikato. The Waitakere Ranges in the west are the remains of a large andesitic volcano, and Great Barrier Island was formed by the northern end of the Coromandel Volcanic Zone. The main isthmus and North Shore are composed of Waitemata sandstone and mudstone, and portions of the Northland Allochthon extend as far south as Albany. Little Barrier Island was formed by a relatively isolated andesitic volcano, active around 1 to 3 million years ago. The Manukau and South Kaipara Harbours are protected by the recent sand dune deposits of the Awhitu and South Kaipara Peninsulas. Recent basaltic volcanic activity has produced many volcanic cones throughout the Auckland Region, including the iconic Rangitoto Island.
Much of Auckland's urban area lies on top of the dormant Auckland Volcanic Field. The region is dotted by 49 volcanoes of varying age with the oldest being in the region of 150,000 years old. The most recent eruption occurred approximately 600 years ago, ending a few hundred years of activity during which Rangitoto Island was formed. Each volcanic eruption has tended to be bigger than the previous, with Rangitoto making up almost 60% of the entire volume of erupted material.
All of the volcanoes are relatively small, most being less than 150 metres (490 ft) in height. A large number of the Auckland volcanoes have been levelled or strongly altered – in small part due to historical Māori use of the cones as fortified pā or for terraced fields, but for most part having been quarried relatively recently for roading and construction materials (mainly scoria). However measures are now in place to preserve many of the remaining volcanoes as landmarks and parks.
Transport in the Auckland Region is predominantly via motor vehicle, with much of New Zealand's motorway-grade roads being located in the region. However, there is also a commuter rail system linking the city centre with Waitakere and Manukau, and a relatively extensive bus system. However, even in the more urbanised parts of the region, public transport uptake is still low (though rising again since the 2000s) compared to many other western cities. Despite this, a significant part of all New Zealand public transport boardings take place in Auckland (see 'Statistics' section below).