Tareahi was born late in the eighteenth century, probably at Te Poraiti, Wharerangi, on the western shores of Te Whanganui-a-Orotū, the inner harbour of present day Napier. As a Ngāti Kahungunu leader, Tareahi inherited his ancestral rights in this district from his mother, Te Huripatu, of Ngāti Hinepare. His father, Waitaringa, belonged to Ngāi Tākaha, a hapū who lived under the mana of Ngāti Te Ūpokoiri, on the upper Ngaruroro River.
In the turbulent period between 1800 and 1830 the tribes of Heretaunga (Hawke's Bay) were either at war with one another or fighting off invaders. In this situation Tareahi developed his warlike character. Because of his fighting qualities he shared the leadership of Ngāti Hinepare with more senior men, Haemania and Pakapaka, the sons of Tarewai. However, some time before 1820 Pakapaka was killed at the battle of Pukemokimoki, on the south side of Ahuriri hill (in present day Napier); he was leading his people against Ngāti Parau. As Pakapaka's elder brother, Haemania, was already dead, it was left to Tareahi to avenge this killing. He did so at the battle of Taitimuroa. Before the battle Tareahi feigned a retreat around a bend of the Tūtaekuri River and stopped to plan his tactics. First he sang a lament for Pakapaka to assuage his grief and rally his warriors. Then he told the Ngāti Hinepare fighting men to advance under cover of darkness and set fire to the enemy canoes. At the same time the Ngāti Te Ūpokoiri warriors approached Pukemokimoki pā from the opposite side. The blazing canoes drew the defenders from the pā, and Tareahi attacked. Many were killed, Pakapaka's death was avenged, and Tareahi was recognised as the principal leader of Ngāti Hinepare.
In the 1820s, when northern invaders were threatening Ahuriri, Te Pareihe, the leader of Ngāti Te Whatuiāpiti, withdrew his followers to Nukutaurua, on the Māhia peninsula. Tareahi, however, remained to support Te Hauwaho of Ngāti Parau. Together they set about strengthening their island fortress, Te Pakake. But, in the battle fought there in the early 1820s, they were no match for the muskets and numbers of Waikato, Ngāti Tūwharetoa, Ngāti Maniapoto and Ngāti Raukawa. There was a massacre and Te Hauwaho was killed. But Tareahi was spared and the prisoners, gathering around him, mingled their tears. Tareahi sang a lament, and urged them to make for his cultivations at Matahourua if they managed to escape. The prisoners, including Tareahi, were taken to the Waikato district, however. Waikato leader Te Wherowhero wept when they arrived, for he knew that the Heretaunga people had been slaughtered without sufficient cause, and he helped to arrange their return. Pāora Kaiwhata, who was with Tareahi, his father, said that they were away for 18 months.
When Tareahi returned, he found the country deserted. He did not, however, join his people at the refuge on the Māhia peninsula, but lived on his land near Lake Ōingo. Thus he kept the fires of Ngāti Hinepare and Ngāti Te Ūpokoiri alight on their lands, and instructed Pāora in the history and customs of the tribe.
Tareahi had several children. His first son, Porokoru Mapu, was born to Hinewhakaehua of Ngāti Kōpua. A daughter, Hēpora, was born to Tareahi and the sister of Hinewhakaehua, Whakahiahia. Tareahi's third wife, Whareunga, of Ngāti Mahu, had three children: Ani Kānara Marewa, who married Pāpaka, younger brother of Mananui and Iwikau Te Heuheu Tūkino; Rāwinia Kāingaroa, who married Pakapaka's grandson; and Pāora Kaiwhata, who was the last tattooed chief of Ngāti Hinepare.
In an era in which few war leaders lived to old age, Tareahi was unusual. He survived to see peace concluded with Ngāti Tuwharetoa, the return of his people to their lands, the coming of Christianity to Heretaunga in the 1840s, and the purchase of the Ahuriri block by the government in 1851.
Tareahi was baptised by the missionary William Colenso in the late 1840s. He took the name Rāwiri, a fitting name for one who, like the psalmist David, was a great warrior and a poet. In 1850 Colenso visited him at Te Poraiti; he found him busy at work making ropes for his fishing nets. Tareahi asked Colenso to baptise the children of the pā, and told the missionary that he always prayed at morning and evening, even when he was alone. Tareahi warned Colenso of hardships ahead. 'Be patient', he said, 'endure hardness'. He may well have anticipated the condemnation that was soon to fall on Colenso for his liaison with a Māori woman.
Donald McLean, at that time a government agent investigating land purchases, met Tareahi in December 1850 at Wharerangi. 'Old Rāwiri, a legendary fixture[,] resides there', he wrote. 'He, his son and wives are now reciting; one of the old men, like the prophet of old, leaning on his staff.'
Rāwiri Tareahi spent his declining days at Te Poraiti pā. He died there, possibly in the 1850s. According to his dying wish, he was buried by his sons within the sound of the sea, below Te Poraiti.