Polynesian settlers of Rēkohu (the Chatham Islands), who developed a distinct culture and language separate from mainland Māori, organised in localised tribal groups (iwi/imi) under the ariki system, and famed for the pacifist covenant of Nunuku-whenua that renounced warfare and man-eating in favour of ritual combat and reconciliation.
Nearly exterminated after the 1835 invasion of the Chathams by Ngāti Mutunga and Ngāti Tama (Taranaki Māori iwi displaced by the Musket Wars), who killed, enslaved, and dispossessed the Moriori; the population fell from roughly 2,000 to 101 survivors by 1862, and the last full-blooded Moriori, Tommy Solomon, died in 1933. The people survive today through descendants of mixed ancestry; the Crown formally apologised and settled Moriori Treaty of Waitangi claims via the Moriori Claims Settlement Act 2021, and the iwi authority (Hokotehi Moriori Trust) continues Moriori cultural and political representation on the Chathams — dates run non-terminal to the present per doctrine for living peoples.
The standard English-language monograph specifically on the Moriori, their culture, and the 1835 invasion and its aftermath; revised edition issued 2000 (ISBN below is the 2000 Penguin paperback, verified via Open Library).