Tainui was one of the great ocean-going canoes in which Polynesians migrated to New Zealand approximately 800 years ago. It was commanded by the chief Hoturoa, who had decided to leave Hawaiki because over-population had led to famine and warfare. The ship first reached New Zealand at Whangaparāoa in the Bay of Plenty and then skirted around the north coast of the North Island, finally landing at Kawhia in the western Waikato. The crew of the Tainui were the ancestors of the iwi that form the Tainui confederation.

Tainui is a tribal waka confederation of New Zealand Māori iwi. The Tainui confederation comprises four principal related Māori iwi of the central North Island of New Zealand: Hauraki, Ngāti Maniapoto, Ngāti Raukawa and Waikato. There are other Tainui iwi whose tribal areas lay outside the traditional Tainui boundaries – Ngāi Tai in the Auckland area, Ngāti Raukawa ki Te Tonga and Ngāti Toa in the Horowhenua, Kāpiti region, and Ngāti Rārua and Ngāti Koata in the northern South Island.