Rereahu was a Māori rangatira (chieftain) of Ngāti Raukawa in the Tainui tribal confederation from the Waikato region, New Zealand.

Rereahu’s father was Raukawa, the son of Tūrongo and Māhina-a-rangi, and a direct male-line descendant of Hoturoa, leader of the Tainui waka.

[4] Rereahu noticed the Ngāti Hā at Te Tīroa while he was foraging for mamaku shoots and reported to his third-cousin Tamāio that they were coming to seize the land.

[5] As a result, Tamāio raised a war party, which advanced on the Ngāti Hā village and drove them out of the region.

[2] They settled in the village called Tihikoreoreo, next to Waimiha,[citation needed] where they had one son: Rereahu later married Hine-au-pounamu, whose parents were Tū-a-tangiroa and a daughter of the Ngāti-Hā chief Hā-kūhā-nui.

[7] Tū-a-tangiroa was a son of Uenuku-tuhatu Uetapu, the older brother of Tamāio’s father Uenuku-te-rangi-hōkā, which meant that Hine-au-pounamu was senior to Rangi-ānewa, which had implications for the relative status of Rereahu’s children.

[13] When Rereahu was on his death-bed he decided to give his mana to Maniapoto, rather than Te Ihinga-a-rangi, because he thought the younger brother had proven himself a better leader.