Wellington Harbour (Māori: Te Whanganui-a-Tara [tɛ ˈfaŋanʉi a taɾa]), officially called Wellington Harbour / Port Nicholson, is a large natural harbour on the southern tip of New Zealand's North Island. The harbour entrance is from Cook Strait. Central Wellington is located on parts of the western and southern sides of the harbour, and the suburban area of Lower Hutt is to the north and east.

The harbour area bounded by a line between Pencarrow Head to Petone foreshore, was officially named Port Nicholson until it assumed its current dual name in 1984.

The earliest known Māori name for the area, Te Upoko o te Ika a Maui, is derived from Māori legend and translates literally as "the head of Māui's fish".

Te Whanganui a Tara, another Māori name for the area, translates literally as "the great harbour of Tara". It is believed to refer to Tara, a son of the Polynesian explorer Whātonga, who was sent down from the Māhia Peninsula by his father to explore southern lands for their people to settle.

Captain James Herd is said to have named the harbour "Port Nicholson" after Sydney's harbourmaster Captain John Nicholson. However, while Herd is attributed as the creator of the first charts describing Te Whanganui a Tara as "Port Nicholson" it is likely that Captain John Rodolphus Kent of the cutter Mermaid had entered the harbour in 1824, and named it after the harbourmaster, his superior officer. A further Māori name for Wellington, Pōneke, is said to be a transliteration of Port Nick (Port Nicholson).

An alternative suggested etymology for the name Pōneke states that it derives from a shortening of the Māori phrase pō nekeneke, meaning "the journey into the night", in reference to the exodus of Te Āti Awa after they were displaced from the Wellington area by the first Europeans. However, the name Pōneke was already in use by February 1842, earlier than the displacement is said to have happened.

William Wakefield is thought to have named the harbour Lambton Harbour in 1839 in honour of the Earl of Durham, who had the family name of "Lambton". Alternatively, it could have been named for the Lambton, a cutter commanded by Captain Barnett, who in 1826 had produced one of the earliest charts of the harbour.

According to oral history, Wellington Harbour was first discovered by the Polynesian explorer Kupe, who visited in the 10th century. A number of place names in the area commemorate Kupe, such as Te Tangihanga o Kupe or Te Raranga o Kupe (Barrett Reef), and Te Aroaro o Kupe or Te Ure o Kupe (Steeple Rock). Kupe also named two islands in the harbour, Mākaro (Ward Island) and Matiu (Somes Island), after his daughters or nieces.

Kupe was followed to the area by Tara and Tautoki, sons of the explorer Whātonga, who settled there. Tara is remembered in the names of both the harbour and the first iwi (tribe) to settle there permanently, Ngāi Tara.

During his voyage on HMS Resolution, James Cook passed by the entrance to the harbour on 2 November 1773, and then put about, in an attempt to see what lay within the entrance. He anchored a mile from Barrett Reef, and made some brief observations noting that it appeared to be a sheltered harbour. A wind change led him to leave the area, and there were no further observations from European explorers for the next 50 years.

In 1826, Captain James Herd entered the harbour on the barque Rosanna, along with Captain Barnett of the cutter Lambton. Both subsequently made charts of the harbour.

The New Zealand Company established settlements in Petone and Wellington from 1840.

The 1855 Wairarapa earthquake uplifted the north-western side of the harbour. This led to reclamation in the harbour, which increased the availability of flat land for Wellington City.

In 1968, the inter-island passenger ferry Wahine grounded at Barrett Reef, near the harbour entrance, during a storm. Fifty-one people died at the time and two more died much later from injuries suffered that day.

According to legend, the harbour of Te Whanganui-a-Tara was created by two taniwha (nature guardian spirits), Whātaitai (or Hataitai) and Ngake. Whataitai lived in the north of the lake where the harbour now is, and was gentle. Ngake, who lived further south, was more violent. Ngake could hear the waters of Raukawa Moana (Cook Strait) pounding to the south, and decided to escape the lake to get to it. He went to the north of the lake to build up his speed for the attempt, then headed off rapidly towards the south. Ngake crashed into and through the rocks at Seatoun and headed out into the Strait. Barrett Reef is said to be the debris left from Ngake's escape. This was seen by Whataitai, who tried to follow Ngake out of the new entrance. The water was now running out of the lake, however, and Whataitai became stranded in the shallows. He stayed there for many generations before being lifted high onto the land by a great earthquake. The soul of Whataitai left him in the form of a bird, Te Keo, and his body formed the isthmus of land where Wellington airport is now located. It flew high above the harbour and wept for the taniwha, whose body was lifted high onto the hills close to the harbour entrance. To this day, Mount Victoria is known to Māori as Tangi Te Keo, "The weeping of Te Keo", and the suburb on the hills immediately below it is named Hataitai.

Another name for the region around the harbour is Te Upoko o te Ika a Māui, which means "the head of Māui’s fish". According to Māori legend, a giant fish was hooked and pulled to the surface by Polynesian navigator Māui and the fish turned into land which became the North Island. The older name is still used in some circumstances for the city or the region, such as the former Māori name of Victoria University of Wellington, which was Te Whare Wānanga o te Ūpoko o te Ika a Māui until 2018.

Wellington Harbour is a natural harbour with an area of around 76 km², with an entrance from Cook Strait at its southern end between Pencarrow Head and Palmer Head on the southern tip of Miramar Peninsula. The harbour has a maximum length of over 11 kilometres and a width of 9.25 kilometres, and the entrance is over 1.6 kilometres wide from shore to shore.

The shipping channel through the harbour entrance lies between Barrett Reef on the western side, and Pencarrow Head to the east. Barrett Reef is a cluster of rocks that is partly exposed even at high tide. It has been the site of a large number of shipwrecks. The most serious loss caused by impact with Barrett Reef is the sinking of the inter-island ferry TEV Wahine in 1968, with the loss of 53 lives.

Wellington Harbour provides sheltered anchorage in a region where wind velocities may exceed 160 km/h. The depth of water over most of the harbour exceeds 20 metres or 10 fathoms.

There are two main bays within the harbour, Evans Bay and Lambton Harbour. The small Oriental Bay to the north of Mount Victoria features beaches and cafes. The suburbs of Wellington city are spread around the low lying terrain immediately surrounding the harbour, and the hills overlooking the west and south-west of the harbour. Lambton Harbour is surrounded by the reclaimed land of Wellington's central business district and contains the majority of the city's port facilities. Evans Bay lies between Mt Victoria and the Miramar Peninsula, and is below the flight path to low-lying Wellington Airport.

To the east of the harbour lie several small bays, most of which are populated by small coastal communities. The largest of these suburban settlements is Eastbourne, directly to the east of the northern tip of the Miramar Peninsula.

The Hutt River enters the harbour at Waiwhetū. In Wellngton city, many small creeks or streams including the Kumutoto, Waitangi and Waipapa streams formerly reached the harbour but were culverted many years ago.

The small islands Matiu / Somes Island, Mākaro / Ward Island and Mokopuna Island are located within the harbour.

The harbour is of seismic origin, and a major earthquake fault line (the Wellington Fault) lies along its western shore. In 2014 another fault line (the Aotea Fault) was discovered extending from Oriental Bay into the harbour. At the northern end of the harbour lies the narrow triangular plain of the Hutt River, which largely follows the line of the earthquake fault to the north-east. The city of Lower Hutt is located on this plain.

Māori oral history recounts that there used to be two channels at the entrance to the harbour. The present entrance was called Te Au-a-Tane and a western channel (now the Rongotai isthmus) was called Te-Awa-a-Taia. Between the two channels lay the island of Motu-Kairangi (present day Miramar Peninsula). Then a violent earthquake known as Haowhenua (Māori for 'land swallower') uplifted the land so that the Te-Awa-a-Taia channel dried up and the island of Motu-Kairangi became joined to the mainland. Researchers have concluded that the earthquake happened around 1460AD.

Although the harbour is almost entirely surrounded by land, several tsunami have been recorded within it. The 1855 Wairarapa earthquake caused a tsunami 3-4-metres high which entered Wellington harbour through the harbour entrance and also straight over the isthmus between Lyall Bay and Kilbirnie. In August 1868, the Arica earthquake in South America causes unusual changes in water levels in the harbour. A gravel bar appeared at Ngauranga, and water almost reached the street at Te Aro. In May 1877, the Iquique earthquake in South America caused water to rush into the harbour, and water levels rose and fell dramatically around the harbour for hours.

The Waiwhetu aquifer is a pressurized zone of water-retaining sand, gravel and boulders beneath the Hutt Valley and Wellington Harbour, which provides around 40 percent of the Wellington region's annual water supply. The harbour basin contains massive quantities of gravel washed down from the Hutt River, in some places hundreds of metres deep. Above the gravel is a layer of mud and silt which seals fresh water within the gravel, creating an artesian aquifer. There are several aquifers in the area in different layers underground, but the Waiwhetu aquifer is the largest and most productive one. Water flows down into the aquifer from a five-kilometre stretch of the Hutt River south of Taita Gorge, and rainwater also contributes to the aquifer. South of Melling the aquifer becomes pressurized by the layer of mud and silt above the gravel layer holding the water in, meaning that if a bore is sunk into the aquifer, water will rise up the pipe. Water from the aquifer also reaches the surface through natural springs at various places around the harbour. Pressure within the aquifer stops sea water from getting into the aquifer.

The water level in Wellington Harbour was much lower 20,000 years ago, and the ancient Hutt River used to flow down a paleochannel to the east of Matiu / Somes Island as far as the present-day Miramar Peninsula. Much of the water in the Waiwhetu aquifer moves under the sea bed from the direction of the Hutt River to the Falcon Shoals area (between Karaka Bay and Worser Bay) at the harbour mouth via the paleochannel. The characteristics of the aquifer between Matiu / Somes Island and the harbour mouth are not as well studied as the portion to the north of the island.

Reclamation of Wellington Harbour started in the 1850s, in order to increase the amount of usable land for the then new City of Wellington. Land plots in the early city were scarce, with little room for public buildings and parks, as well as inadequate dockside areas for shipping. Reclamation progressively advanced into the harbour throughout the 19th and 20th centuries, providing room for public, commercial and industrial areas for the city.

Fish species commonly caught in the harbour by recreational fishers include red cod, kahawai, gurnard, tarakihi, snapper, trevally, elephant fish and kingfish. Children enjoy catching spotties. Eagle rays and stingrays can both be found in the harbour: eagle rays are often seen in the shallow water around Whairepo Lagoon, which was named after the Māori name for the species. Several species of octopus live in the harbour. In the late nineteenth and early twentieth centuries, large octopuses would occasionally grab people at the water's edge. Rig sharks visit the harbour each year to mate and give birth. Other species seen less often include basking sharks, blue sharks and seven-gilled sharks.

Common dolphins and orca visit the harbour quite often. In the nineteenth century, southern right whales bred within Wellington Harbour, but in the 21st century sightings are rarer. Humpback whales are also seen occasionally. There is a fur seal colony at Pariwhero / Red Rocks on the south coast facing Cook Strait, and seals sometimes appear in and around the harbour. Vagrant and rare marine mammal visitors include leopard seals (reclassified from vagrant to resident in 2019), crabeater seals, and an elephant seal nicknamed 'Blossom' that hung around the harbour for several years in the 1960s.

Over 100 species of seaweed are found in Wellington Harbour. Rocky shores around the harbour support kelp forests, for example at Kau Bay, but rising sea temperatures may be affecting the health of these areas. Sponge beds are found in deeper parts of the harbour.

Between 2018 and 2022, annual surveys were made of indigenous coastal birdlife along the coastlines of the south coast and the western side of Wellington Harbour. Thirty-four native or endemic species and 14 naturalised introduced species were observed, though some of these were only seen on the south coast and not within the harbour. The surveys showed that stretches of the coastline "hardened" by reclamation or seawall construction have lower densities of birds and less diversity of species, probably due to the steepness of the shoreline and lack of intertidal foraging habitats. Changes to average sea level and temperature may affect some species in the future. Black-backed gulls, red-billed gulls and several species of shags are found all around the harbour. A breeding population of fluttering shearwaters has been established on Matiu / Somes Island. Little blue penguins are found in many locations, with nesting boxes provided in some places to encourage them.

As part of maintaining a healthy marine environment, Greater Wellington Regional Council and the National Institute of Water and Atmospheric Research (NIWA) have monitored water quality in Wellington Harbour since 2016. Water quality is affected by sediment, nutrients and pollutants from the whole catchment around the harbour, turbidity caused by rainfall and outflow from the Hutt River, and tides.

The Ministry of Agriculture and Forestry and NIWA have carried out surveillance on non-indigenous marine species which may arrive in the harbour in water ballast or attached to hulls of ships. Examples of marine pests found in the harbour include the Northern Pacific sea star and wakame, a seaweed native to the north-west Pacific Ocean, which was first found in Wellington Harbour in 1987. It grows rapidly and can displace native species of seaweed.

Volunteers from the group Ghost Diving organise regular harbour clean-ups, collecting tonnes of rubbish from the water around the inner-city waterfront and bringing attention to the problem of littering.

Wellington Harbour is a significant port serving the lower North Island, with the Regional Council-owned company CentrePort recording around 14,000 commercial shipping movements each year. Wellington Harbour, the region's third largest container port, is located in Wellington City. There is a tanker terminal at Seaview in Lower Hutt.

Wellington harbour ferries first began operating at the end of the 19th century and regular crossings from central Wellington to Days Bay continue today. The harbour is also used by inter-island ferries linking Wellington to Picton.

A project to develop a walking and cycling route around the harbour, the Great Harbour Way, is gathering momentum. Te Ara Tupua is a cycling and walking path being built from Melling in the Hutt Valley to central Wellington.

As of 2024, there are 20 wharves situated around Wellington Harbour. This includes large wharves in the inner harbour and port area, smaller wharves in seaside suburbs and the fuel wharves at Point Howard and Evans Bay. The first wharves were built from 1840 by newly-arrived European settlers, to enable them to move goods from ship to shore. The first publicly-owned wharf built in Wellington Harbour was Queens Wharf, completed in 1862. In 1880 the Wellington Harbour Board was created and took control of most wharves in the harbour until its disestablishment in 1989.

At that time a commercial company, Port of Wellington (now called CentrePort Wellington) took over management of most industrial wharves, while Wellington City Council and Hutt City Council gained control of most suburban wharves. Wharves were built for various purposes – moving fuel, primary products such as timber, wool and meat coming from the hinterland, other goods and passengers. Wharves for passenger ferries included ferries taking commuters and day trippers to and from the city and suburbs, and larger inter-island ferries going to Picton and Lyttelton. The wharves also serviced passenger liners from overseas, and TEAL flying boats. Over time Wellington's wharves have been altered, upgraded, extended, truncated or buried in reclamation along the shoreline of Wellington Harbour. Many wharves have been repurposed in response to changing domestic and international conditions and requirements for maritime transport of passengers and cargo.

Wellington's south coast and harbour entrance are exposed to open sea, providing places to dive and fish. There are also fishing spots at the rocks and reclamations within the harbour.

Harbour beaches like Oriental Bay, Petone, Days Bay and Hataitai Beach are suited to swimming and sunbathing.

The harbour accommodates a range of activities, with five water ski lanes, an area for personal water craft and areas for windsurfing. Several rowing, waka ama and yachting clubs operate from the harbour.

Small boat craft can anchor at Mākaro / Ward Island and Mokopuna Island and can also visit the Matiu / Somes Island reserve during daylight hours. Harbour cruises also travel regularly between the main Wellington waterfront, Matiu / Somes Island, Days Bay and Petone.

In 1974, the New Zealand author Denis Glover published the anthology Wellington Harbour, containing poems about or inspired by views of the harbour.

Big weather is an anthology of 100 poems about Wellington's harbour, hills, and environment. It was published in 2009 and in later editions.

The Wellington Writers Walk is a series of 23 quotations from New Zealand poets, novelists, and playwrights, installed along the Wellington waterfront in the form of contemporary concrete plaques or inlaid metal text on wooden 'benchmarks'. The plaques celebrate the lives and works of these well-known writers, all of whom had (or have) some connection to Wellington. Many of the quotations reference the harbour.

• 
  HMS Indefatigable, 1945
• 
  MS Wanganella being towed from an entrance reef, 1947
• 
  QE2 slips out the entrance in a following breeze, 2006
• 
  Tugs Kupe and Toia, 2006
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  Lambton Harbour, 2007
• 
  HMNZS Canterbury, 2007
• 
  Aotea Quay, 2008
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  Ferry and Barrett Reef just after low water, 2010
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  Aotea Quay, Queen Mary 2, 2011
• 
  Pleasure craft, 2012

• Reclamation of Wellington Harbour
• Notable ship visits to Wellington
• Miramar Peninsula
• Evans Bay
• Porirua Harbour

• CentrePort Wellington
• Positively Wellington Waterfront
• Greater Wellington Regional Council