Its takiwā (tribal area) is the largest in New Zealand, and extends from the White Bluffs / Te Parinui o Whiti (southeast of Blenheim), Mount Mahanga and Kahurangi Point in the north to Stewart Island / Rakiura in the south.

Some European settlers intermingled with native iwi populations, and today, most families who descend from Ngāi Tahu also have Ngāti Māmoe and British ancestry.

Ngāi Tahu trace their traditional descent from Tahupōtiki (also Te Tuhi-māreikura-ooho-a-tama-wahine), and Tahumatua[citation needed]), the younger brother of Porourangi.

[citation needed] As according to ancient protocol, he took Porourangi's grieving wife Hamo-te-rangi as his own, by whom he had at least four sons: Ira-a-Tahu, Ira-(apa)-roa,[8] Tahumuri-hape, and Karimoe.

[citation needed] Tahupōtiki, Ira-a-Tahu, Iraroa, and Tahumuri-hape moved south towards Tūranga, then settled at Maraetaha at the northern end of the Wharerātā Range.

[citation needed] Owing to growing tensions between the various iwi inhabiting the surrounding area, many groups began their migration away from Waerenga-a-Hika in the Gisborne District.

[2] Perhaps a more notable instance, is when Rākaihikuroa's other son Rākaipaaka was insulted by local Chief Tūtekohi who had invited him to his pā and then fed the prepared feast to his kurī (dog) Kauerehuanui.

The ancestress Tūhaitara, senior granddaughter of Rakawahakura, insulting her husband Chief Marukore of Ngāti Māmoe,[7][11] or Te Kāhea,[10] and his ancestry, as well as various other exchanges are the reason for war between their two iwi.

[11] However, Marukore knew of their plan and defeated them in the Battle of Hūkete after which their sister Hinehou laid them on the floor of her whare for her grandchildren to see, and left her belongings with them before burning down the building in an incident now known as Kārara Kōpae ("The Laying Down of Fighting Chiefs").

As they were about to take advice from a local chief named Rākaimoari, his daughter Hinewai-a-tapu made a remark about Tahumatā which sparked the Battle of Te Pakiaka ("The Roots") that lasted for some days.

[9] In Wellington Te Aohikuraki, the senior chief, slept with Rākaitekura (a high ranking Ngāi Tahu woman) while her husband Tūmaro was away visiting his family.

Upon his arrival to Waimea, Tūmaro's father Kahukura-te-paku, not knowing who he was, had intended to cannibalise him, but later put a stop to the meal preparations when local children heard Te Hikutawatawa muttering of his origins.

[14] Late in the 17th century the iwi began migrating to the northern part of the South Island under the leadership of the Ngāti Kurī chief Pūrahonui, with his sons Makō-ha-kirikiri and Marukaitātea, establishing the Kaihinu pā in the Tory Channel / Kura Te Au.

For this Ngāti Māmoe then ceded the east coast regions north of Waiau Toa to Ngāi Tahu, and Tūteurutira and Hinerongo married and settled at the pā.

At the Pariwhakatau pā near the Conway area, Makō-ha-kirikiri was with his sisters Te Apai and Tokerau, Manawa-i-waho's wives, when Tukiauau sneaked in and killed Manawa.

As a consequence for ignoring Chief Te Aweawe's advice to strap two canoes together for a safer passage, Tūāhuriri is said to have been left to drown along with Tūmaro while trying to leave Wellington.

He destroyed Ngāti Māmoe's pā at Mānuka, across the hills at Taitapu, and prior to that also lived at Te Pā-o-Te Rakiwhakaputa on the Cam River / Ruataniwha for a time.

Chief Huikai also established himself at Koukourarata (named after the stream in Wellington where Rākaitekura prepared her hair), and his son Tautahi took Ōtautahi (the site of present-day Christchurch).

[22] Makō-ha-kirikiri of Wairewa and Moki both avenged the deaths near where the bodies were found in the water, on the shores of Lake Mahinapua in the battle called Tāwiri-o-Te Makō.

[22][28][29] The Kaihuānga feud of the 1820s heavily involved the upoko ariki (paramount chief) Tamaiharanui, whose status was so spiritually superior within the iwi that people of lower ranking would avert their gaze and avoid looking at him directly.

The feud sparked when a woman from the Waikakahi pā at Wairewa named Murihaka wore a dogskin cloak which belonged to Tamaiharanui, thus causing an insult to him.

The Taumutu then asked the hapū of Otago for assistance, to which Taiaroa and Te Whakataupuka led a taua, and along with warriors from Kaiapoi, all attacked Waikakahi.

[29] In November 1830 Te Rauparaha persuaded Captain John Stewart of the brig Elizabeth to carry him and his warriors in secret to Takapūneke near present-day Akaroa, where by subterfuge they captured Tamaiharanui and his wife and daughter.

In 1834 Chief Iwikau, brother of Te Maiharanui, led a war party into the Marlborough Sounds, though Ngāti Toa had hidden from them and could not be found.

Tūhawaiki had by now learned of this oncoming attack, and led his own taua from Ruapuke Island to Tuturau, where he fought and killed Te Pūoho.

[35] At the very end of the 19th century a Ngāi Tahu man named William Timaru Joss (1844–1895), a Stewart Island whaler and captain of the mailboat Ulva,[38] was a member of the first confirmed landing party of the Antarctic on the continent of Antarctica at Cape Adare, along with Captain Kristensen, Bull, Borchgrevink, and Tunzelmann in January 1895,[39] making Joss the first known Māori to get so close to the continent.

A handful of notable servicemen included: Turu Rakerawa Hiroti, Hoani Parata, James William Tepene, and John Charles Tamanuiarangi Tikao, all of whom held the rank of captain.

[47] A core contributor to the degradation of water quality has been the growth of intensive dairy farming over three decades which has left many South Island rivers with deficient streamflows and problematic nitrate‑based eutrophication.

Ngāi Tahu has a very corporate structure, in part due to the death of an important upoko ariki (paramount chief), Te Maiharanui, at the time of the arrival of Europeans in New Zealand.[why?]

The kaiwhakahaere (chairperson) from 2016 was Lisa Tumahai, the chief executive officer is Arihia Bennett, the general counsel is Chris Ford, and the trust is based in Addington, Christchurch.