Ngāi Tahu, or Kāi Tahu, is the principal Māori iwi (tribe) of the South Island. Its takiwā (tribal area) is the largest in New Zealand, and extends from the White Bluffs / Te Parinui o Whiti (southeast of Blenheim), Mount Māhanga and Kahurangi Point in the north to Stewart Island / Rakiura in the south. The takiwā comprises 18 rūnanga (governance areas) corresponding to traditional settlements. According to the 2023 census an estimated 84,000 people affiliated with the Kāi Tahu iwi.
Ngāi Tahu originated in the Gisborne District of the North Island, along with Ngāti Porou and Ngāti Kahungunu, who all intermarried amongst the local Ngāti Ira. Over time, all but Ngāti Porou would migrate away from the district. Several iwi were already occupying the South Island prior to Ngāi Tahu's arrival, with Kāti Māmoe only having arrived about a century earlier from the Hastings District, and already having conquered Waitaha, who themselves were a collection of ancient groups. Other iwi that Ngāi Tahu encountered while migrating through the South Island were Ngāi Tara, Rangitāne, Ngāti Tūmatakōkiri, and Ngāti Wairangi – all of which also migrated from the North Island at varying times. During the 19th century, hundreds of thousands of Europeans – mostly British – migrated to New Zealand. After European arrival, Ngāti Toa (allied with Ngāti Tama) and Ngāti Rārua invaded Ngāi Tahu's territory with muskets. Some European settlers intermingled with native iwi populations, and today, most families who descend from Ngāi Tahu also have Ngāti Māmoe and British ancestry.
