Hamiora Mangakahia, also called Tana and later Piripi, is said to have been born in 1838 at Waikaurau, which was probably at Whangapoua Harbour on the eastern Coromandel Peninsula. His mother was Riria Poau (Ponau) of Whangapoua. Because of wars between her people and Nga Puhi, she had been born and brought up on Tuhua (Mayor Island), where she met Hamiora's father, Piripi Te Aue Te Ikatoroa, of Ngati Kahungunu. He had been captured, probably by Ngati Maru in the 1820s. After intertribal fighting died down in the 1830s, Riria took her family back to Whangapoua. Hamiora Mangakahia was descended from Ngati Maru and Ngati Tama-Te-Ra, but his most important link was to Ngati Whanaunga. His hapu were Ngati Hei and Ngati Pare. He claimed land as Ngati Huarere, the earlier inhabitants of the Coromandel Peninsula.
Mangakahia was exposed from childhood to the new commercial world arising from contact with Europeans; his mother and her cousin Te Ngarahu arranged the early timber contracts at Whangapoua. As a youth he lived for some years with his father's cousin Wi Paekohe in Poverty Bay. In 1862 he was trained in genealogy and tradition by elders at Whareongaonga. Although he was probably a Christian from an early age and later belonged to the Mormon church, he was also a pupil of the tohunga and prophet Toiroa at Nukutaurua on the Mahia Peninsula, and considered himself bound to carry on the prophet's teaching after his death in 1867. From his brother, Mohi, who had been deprived of much of his land, Mangakahia learned a profound and lasting distrust of Europeans. Mohi, who was a Native Land Court agent and involved in politics, was expected to stand for election to the Western Maori seat in Parliament in 1876, but died in 1875. Hamiora Mangakahia was the heir to both his brother's influence and his problems.
Hamiora Mangakahia married three times. The name of his first wife is not known. His second wife was Puriake or Pauaka of Ngati Awa, the mother of his eldest son, Hamiora Whakakoro Mangakahia, and of a daughter. Father and son became estranged in later years. Mangakahia married again, probably in the late 1880s or early 1890s. His third wife was Meri Te Tai of Te Rarawa. They had two sons, Mohi and Waipapa, and two daughters, Whangapoua Tangiora Edith and Mabel Te Aowhaitini.
Throughout his life Mangakahia was plagued by Europeans anxious to profit from his Whangapoua lands, valued for their kauri and other timber. His battles with the Kauri Timber Company, the New Zealand Timber Company and the solicitor Frederick Earl were generally unsuccessful, resulting in the transfer of his interests to his mortgagees. Efforts from 1914 to 1916 to succeed to Wi Paekohe's interests in land around Gisborne and in Portland Island were also unsuccessful. At the time of his death, of all the thousands of acres once controlled by his family, Mangakahia retained only one major block.
For a time Mangakahia felt the only solution to Maori economic problems was to abandon Maori customs of hospitality, as the proceeds of land sales were being consumed by chiefly extravagance. His own unhappy experiences with land matters made him a shrewd counsel in the Native Land Court, where he not only represented his own kin, but was invited to conduct cases as far afield as Cambridge, Alexandra (Pirongia) and Napier. He also became an assessor of the court, practising at hearings across the country, including Maketu, Mokau, and some of the various hearings into the Horowhenua block. In 1891 Mangakahia was one of few Maori whose views were sought in Auckland, and again at Waipawa, by the Maori Land Laws Commission. He advocated setting up a tribunal with powers to settle all outstanding land disputes between Maori and Europeans, and the repeal of all legislation in connection with the Native Land Court.
Hamiora Mangakahia's greatest political achievement was his contribution to Te Kotahitanga, the Maori parliament movement. He was at the Bay of Islands in 1889 when Nga Puhi formally initiated an attempt to forge the political union of the North and South Island Maori tribes, and was among the first signatories of the movement's deeds of union. Mangakahia was selected by Heta Te Haara to explain the purpose of the union to delegates at the preliminary session held at the meeting house Te Tiriti o Waitangi at the Bay of Islands in April 1892. Mangakahia explained that the movement hoped to establish a Maori government to control Maori land and other matters. Such an institution was authorised by section 71 of the 1852 constitution, he claimed, and it would be the executive arm of a national Maori union under the authority of the Treaty of Waitangi. The treaty established the Queen's authority over the whole country but also established that Maori alone had authority over their lands. Under Maori custom, Mangakahia pointed out, one authority would never encroach on another. He also stated that if the movement provoked serious trouble between Maori and Europeans it would have to be abandoned.
On 20 April 1892 Mangakahia was appointed to a committee to reconsider the movement's aims. Its report advocated the abolition of the Native Land Court and its Maori assessors, and all related legislation. Maori committees should be established to consider lands still under Maori title; land court sessions, with the exception of rehearings, were to be boycotted. By the end of the preliminary session Mangakahia, working alone, prepared all the documents for the first sitting of the Maori parliament, to be held at Waipatu in June 1892. On 17 June, nominated by Henare Tomoana and Te Keepa Te Rangihiwinui, Mangakahia was elected premier of the Great Council (the lower or elected house). Four days later he presented a bill requesting that a petition be sent to the colonial parliament asking that all legislation on Maori land and people cease, and that Maori be empowered to make their own laws.
Mangakahia was not re-elected for the second sitting of the Maori parliament in 1893, but continued to be called on for advice. His plain speaking may have caused offence, for in April the Council of Paramount Chiefs (the upper house) was considering his expulsion from the movement, but on 1 May he was sworn in as a member of the Great Council. He told the house that he was willing to stand for the colonial parliament, and that he had given up an annual income of £500, a sum which included his salary as Native Land Court assessor, in order to devote himself to the work of Te Kotahitanga.
Mangakahia was re-elected premier at the fourth session, held at Rotorua in 1895. This session was noted for the obstruction by Henare Tomoana, who styled himself leader of the opposition and attempted to force Mangakahia's resignation on the grounds that Te Kotahitanga funds had been mismanaged. Mangakahia, with support from many other chiefs, was able to show that the movement's financial problems had developed under the premiership of his successor in 1893, Te Whatahoro Jury.
Apart from personal ambitions, the issues between Mangakahia and Tomoana reflected a growing split in the Kotahitanga movement, which was never to be resolved. Mangakahia represented those who refused to accept a moderate line acceptable to the colony's government. This split grew out of two bills asking for separate powers for Maori, presented by Hori Kerei Taiaroa and Hone Heke. Taiaroa's bill sought power of assembly for the Kotahitanga parliament which would pass bills that the governor would sign into law. Mangakahia favoured Heke's bill, which asked for separate Maori institutions and excluded the governor.
Although still officially premier in 1897, Mangakahia was prevented from attending either the April or October sessions by the death on 17 April of his 26-year-old daughter from his second marriage, and by a severe attack of rheumatism. In March 1898, still premier, he claimed in Te Puke ki Hikurangi that between 13 March 1889 and 6 October 1897 the Kotahitanga deeds had been signed by 37,000 Maori. He warned the people that the colonial government had mortgaged the country to English interests, and advised them to hold fast to the Treaty of Waitangi, to the 71st clause of the 1852 constitution, and to the Kotahitanga deeds they had signed.
The split within Te Kotahitanga became more obvious after the moderate party, led by Tomoana and Tamahau Mahupuku, succeeded in having the 1897 and 1898 sittings of the parliament transferred to Papawai. The issue now became the Native Lands Settlement and Administration Bill. It was promoted at Papawai by the premier, Richard Seddon, who promised that if Parliament passed this bill the government would purchase no more Maori land, and would not permit Europeans to do so. Mangakahia's party regarded the bill's provisions as paternalistic, and he explained their objections at meetings with Seddon in Wellington in July 1898. Land given up to the proposed boards would effectively be controlled by the government, the boards' expenses would swallow up the revenue, and all that would be left to the owners of the land would be their names on a piece of paper. He and others collected 9,775 signatures to their petitions declaring their opposition to the bill.
Mangakahia spent most of his later years at Te Pungapunga, Whangapoua, attempting to settle his private affairs. In 1907 he attended a meeting at Waahi, Huntly, organised to discuss Maori grievances arising from breaches of the Treaty of Waitangi, and to form a new union under the authority of the treaty and the 1852 constitution. The resurrected Kotahitanga would enable a united Maori appeal to the imperial government. Mangakahia reminded the meeting of earlier efforts, and approved of the plan to send a deputation to England, but it failed to go ahead as he had hoped.
Mangakahia was at Papawai again in 1911, but this would have been one of his last excursions; he was in a wheelchair in his last years. According to family information, he died on 4 June 1918, and was buried on a knoll above his homestead at Whangapoua.