Te Rangitahau, often known as Tahau, was born probably in the late 1820s or early 1830s near Opepe, 10 miles south-east of Tapuaeharuru (Taupo). His descent was from Ngati Hineuru, and from Ngati Kurapoto and Ngati Maruwahine, now regarded as hapu of Ngati Tuwharetoa. His mother was Parekaui, and his father was (probably) Ngawaka. Little is known of his early life, spent at Opepe, but in adulthood he made a formidable warrior: reportedly six feet four inches tall and about twenty-four stone. He was a pupil of the renowned tohunga Werewere Te Rangipumamao of Tapuaeharuru. When, in his early manhood, he became a leader of his people, his influence extended at least from Waipahihi to present-day Waitahanui, possibly as far south as Korohe, and eastwards to Opepe.
Te Rangitahau emerged as an adversary of the colonial government when, in October 1866, he accompanied about 100 Ngati Hineuru under Te Rangihiroa to Omarunui in Hawke's Bay; it was thought that they intended to attack Napier, so they themselves were attacked and defeated by Colonel George Whitmore. Te Rangitahau and others were deported to Wharekauri (Chatham Island).
In July 1868 Te Rangitahau was among the group of prisoners led by Te Kooti who escaped from Wharekauri; they captured the schooner Rifleman and sailed to Poverty Bay. He became one of Te Kooti's most loyal lieutenants, taking part in the initial actions at Paparatu, Te Koneke and Ruakituri when government forces attempted to prevent Te Kooti from leaving the coastal area. Te Kooti soon launched a series of reprisal raids against Pakeha settlers and Maori on the East Coast. Te Rangitahau was one of the leaders of the attack on Major Reginald Biggs's house during the raid on Matawhero on 10 November 1868.
Te Rangitahau withdrew into Urewera with Te Kooti following their escape from the siege of Ngatapa in January 1869. He re-emerged on 9 March along with a rebuilt force under Ngati Tuwharetoa chief Wirihana Koikoi, who led the attack on Ngati Pukeko near Whakatane. He was also one of the leaders of a raiding party sent to Uretara Island near Ohiwa where Robert Pitcairn, a surveyor, was killed. After further skirmishing the force travelled to Hawke's Bay and attacked Ngati Pahauwera of Mohaka on 10 April 1869, taking the lives of at least 57 Maori and seven Pakeha. Te Rangitahau became notorious for his prominent part in the killings.
Te Kooti's forces then crossed the western arm of Lake Waikaremoana and returned to Urewera; after further skirmishes against government troops they descended to the Rangitaiki plains, east of Taupo. A new campaign began in this area. Te Rangitahau helped to guide Te Kooti's forces to Lake Taupo and led an advance party during the brilliantly executed stratagem which, at Opepe on 7 June, resulted in the deaths of nine volunteers from the government forces; five others escaped. This raid served to announce dramatically the arrival of Te Kooti in Ngati Tuwharetoa territory. It unsettled the government and its Maori allies of Tapuaeharuru, and contributed to the demoralisation of government forces in the Bay of Plenty region.
Te Kooti next intended to exact revenge on northern Ngati Tuwharetoa for their support of the government. He would then cement an alliance with the sympathetic southern Ngati Tuwharetoa hapu, gain King movement support and defeat the government forces in battle. This plan brought about the defection of Te Rangitahau for reasons that remain unclear. According to one version of events, he protested at Te Kooti's intention because the northern Ngati Tuwharetoa were his relatives. He reminded Te Kooti of his agreement that whenever they happened to be in a district belonging to any chief who had joined him, that chief should have a voice in the operations. Another version of this pact has it that when they fought against Te Kooti's people on the East Coast, Te Rangitahau was to do the killing, but when they were in Ngati Tuwharetoa territory, Te Kooti was to have the responsibility. When they reached the Taupo area, Te Rangitahau did not honour the agreement; instead, he warned his people between Waipahihi and Korohe (and possibly those of Tapuaeharuru) to flee. As a consequence of the betrayal Te Kooti and Te Rangitahau may actually have fought each other.
It is probable that Te Rangitahau took no part in Te Kooti's final stand at Te Porere on 4 October 1869. He may have returned to Opepe, keeping out of further unrest and not attacking any other settlers. It is also possible that he was in the Bay of Plenty. Gilbert Mair recorded that Te Rangitahau and 30 men sought refuge at Ohinemuri with Te Hira, a chief of that region. He was also seen in 1870 at Katikati heads as the chief of a party of 60 'Hauhau' fishermen; he was reported as seeming less bellicose and his group as looking 'well and healthy'.
Te Rangitahau's absence from the Taupo campaigns made Te Kooti's military objectives more difficult to achieve. He had been, in a sense, Te Kooti's passport through the Taupo area, and his departure left Te Kooti in a vulnerable position in a land of hostile tribes and troops determined to defeat him. The only Ngati Tuwharetoa remaining with Te Kooti were those with Horonuku Te Heuheu, who may not have been strongly committed to Te Kooti's cause.
Te Rangitahau was regarded as being energetic and fearless in battle. He was accused of callousness in the execution of prisoners, although that is also true of some Maori who fought for the government. His descendants regard him as a staunch fighter with Te Kooti against a common enemy. Nevertheless, loyalty to his own people was ultimately stronger than the desire to serve the charismatic guerrilla leader. Te Rangitahau's mana and power, which may have ensured a degree of autonomy for him within Ngati Tuwharetoa politics, may have allowed him to place the safety of his people ahead of his sympathy with Te Kooti's objectives. Perhaps, too, his decision was influenced by pressure from the chiefs of Tapuaeharuru.
Te Rangitahau was living at Taupo in the 1880s, when he gave evidence to Native Land Court hearings. He succeeded in having his name inserted in the list of grantees of the Pohokura block. One account says that he had two sons, Te Ranginui and Paoro, and that his widow, whose name is unknown, was living at Waitahanui about 1910. In 1900, Te Rangitahau visited Rotorua to perform a tapu-raising ceremony on a carved house. The Ngati Awa tohunga, Hamiora Tumutara Pio, also took part in the ceremonies. It is said that their rival powers were so great that Te Rangitahau died a few days after the ceremony, and Pio shortly thereafter.