An ariki (New Zealand, Cook Islands), ‘ariki (Easter Island), aliki (Tokelau, Tuvalu), ali‘i (Samoa,Hawai‘i), ari'i (Society Islands, Tahiti), aiki or hakaiki (Marquesas Islands), akariki (Gambier Islands) or ‘eiki (Tonga) is or was a member of a hereditary chiefly or noble rank in Polynesia.
Political leadership or governance in Māori society has traditionally come from two different groups of people – the ariki and the rangatira. The ariki are the "persons of the highest rank and seniority". As the "high-ranking first-born children of first-born children", ariki inherit their positions from their forebears. In particular, their "supreme rank [comes] from the conjunction of a number of senior descent lines from founding ancestors, and ultimately from the gods". Although most ariki in the past have been male, women, like Te Atairangikaahu, have "brought their own qualities to bear on leadership ... [with] the expectations of them ... [being] the same as for men".
Ariki do not operate in simple hierarchical organisations; despite what "government officers were inclined to believe", ariki have never been "the apex of a structured hierarchy of institutionalised tribal authority". Many positions overlap with ariki holding multiple roles, including "head of an iwi, the rangatira of a hapu and the kaumatua of a whanau". Similarly, in times past, "a tohunga may have also been the head of a whanau but quite often was also a rangatira and an ariki".