Mount Taranaki (Māori: Taranaki Maunga), formerly Mount Egmont, is a dormant stratovolcano and legal person in the Taranaki region on the west coast of New Zealand’s North Island. At 2,518 metres (8,261 ft), it is the second highest mountain in the North Island, after Mount Ruapehu. It has a secondary cone, Fanthams Peak (Māori: Panitahi), 1,966 metres (6,450 ft), on its south side.

The name Taranaki is from the Māori language. The mountain was named after Rua Taranaki, the first ancestor of the iwi (tribe) called Taranaki, one of several iwi in the region.The Māori word tara means mountain peak, and naki may come from ngaki, meaning “clear of vegetation.”It was also named Pukehaupapa (“ice mountain”) and Pukeonaki (“hill of Naki”) by iwi who lived in the region in “ancient times”.

Captain Cook named it Mount Egmont on 11 January 1770 after John Perceval, 2nd Earl of Egmont, a former First Lord of the Admiralty who had supported the concept of an oceanic search for Terra Australis Incognita. Cook described it as “of a prodigious height and its top cover’d with everlasting snow,” surrounded by a “flat country … which afforded a very good aspect, being clothed with wood and verdure”.

When the French explorer Marc-Joseph Marion du Fresne saw the mountain on 25 March 1772 he named it Pic Mascarin. He was unaware of Cook’s earlier visit.

It appeared as Mount Egmont on maps until 29 May 1986, when the name officially became “Mount Taranaki or Mount Egmont” following a decision by the Minister of Lands, Koro Wētere. The Egmont name still applies to the national park that surrounds the peak and geologists still refer to the peak as the Egmont Volcano.

As part of the Treaty of Waitangi settlement with Ngā Iwi o Taranaki, a group of tribes in the region, the mountain will be officially named Taranaki Maunga, and will be the first natural geographic feature with an official name in Māori, rather than English.The settlement was initialled on 31 March 2023, and has been ratified by the iwi of Taranaki.

Some iwi in the region had referred to the mountain as Taranaki Mounga rather than Taranaki Maunga, per the local Māori dialect.

Mount Taranaki is situated in the sedimentary Taranaki Basin and is part of the Taranaki Volcanic Lineament which has had a 3 cm/year (1.2 in/year) north to south migration over the last 1.75 million years. A Wadati–Benioff zone exists at about 200 km (120 mi) depth and the volcano’s magma has the geochemical features of an arc volcano. Under the volcano itself there is high heat flow with only about 10 km (6.2 mi) crustal thickness although this rapidly normalises for continental crust to 35 km (22 mi) east of the volcano and 25 km (16 mi) to the west.

Taranaki is geologically young, having commenced activity approximately 135,000 years ago. The most recent volcanic activity was the production of a lava dome in the crater and its collapse down the side of the mountain in the 1850s or 1860s. Between 1755 and 1800, an eruption sent a pyroclastic flow down the mountain’s northeast flanks, and a moderate ash eruption occurred about 1755, of the size of Ruapehu’s activity in 1995/1996. The last major eruption occurred around 1655. Recent research has shown that over the last 9,000 years minor eruptions have occurred roughly every 90 years on average, with major eruptions every 500 years. Some of these eruptions may have occurred with very brief warning, of only days or less.

Taranaki is unusual in that it has experienced at least five of its major eruptions by the method of cone collapse. Few volcanoes have undergone more than one cone collapse. The vast volume of material involved in these collapses is reflected in the extensive ring plain surrounding the volcano. There is also evidence of lahars being a common result of eruption. The major collapse cycles have a potential maximum size of collapse of 7.9 km³ (1.9 cu mi) every 30,000 to 35,000 years. Such collapse debris fields have been found up to 5–6 km (3.1–3.7 mi) beyound the coast. Another major edifice collapse is expected to occur within 16,200 years.

Much of the region is at risk from lahars, which have reached the eastern coast. A volcanic event is not necessary for a lahar: even earthquakes combined with heavy rain or snow could dislodge vast quanтιтies of unstable layers resting on steep slopes. Many farmers live in the paths of such possible destructive events.

Although volcanic eruptions are notoriously chaotic in their frequency, some scientists warn that a large eruption is “overdue”. Research from Mᴀssey University indicates that significant seismic activity from the local faults is likely again in the next 50 years and such might be permissive to an eruption. What ever in the next 50 years, the probability of at least one eruption is between 33% and 42%. Prevailing winds would probably blow ash east, covering much of the North Island, and disrupting air routes, power transmission lines and local water supplies.

Mount Taranaki is one of four closely ᴀssociated Quaternary volcanoes in Taranaki province that have erupted from andesite magmas that have not extensively ᴀssimilated enriched crust unlike the cone volcanos of the North Island Volcanic Plateau. It sits on the remains of three older volcanic complexes that lie to the northwest. The Indo-Australian Plate is slowly moving relative to the magma source that feeds these volcanoes. This trend is reflected in Fanthams Peak, the newer secondary cone on the southeast side of Taranaki and named after Fanny Fantham who was the first European woman to climb the peak in 1887.

The oldest volcanic remnants consist of a series of lava plugs: Paritutu Rock (156 metres), which forms part of New Plymouth’s harbour, and the Sugar Loaf Islands close offshore. These have been dated at 1.75 million years.

On the coast, 15 kilometres southwest of New Plymouth is the Kaitake Range (682 metres), last active over 500,000 years ago.

Nearest to Taranaki is the Pouakai Range. Pouakai may have originated around the same time as Kaitake but remained active until about 210,000 years ago. Much of Pouakai’s large ring plain was obliterated by the Egmont Volcano, the hills near Eltham being the only remnant to the south.