Te Rangitāhau, often known as Tāhau, was born probably in the late 1820s or early 1830s near Ōpepe, 10 miles south-east of Tapuaeharuru (Taupō). His descent was from Ngāti Hineuru, and from Ngāti Kurapoto and Ngāti Maruwahine, now regarded as hapu of Ngāti Tūwharetoa. His mother was Parekaui, and his father was (probably) Ngāwaka. Little is known of his early life, spent at Ōpepe, 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 Rangipūmamao of Tapuaeharuru. When, in his early manhood, he became a leader of his people, his influence extended at least from Waipāhīhī to present-day Waitahanui, possibly as far south as Kōrohe, and eastwards to Ōpepe.
Te Rangitāhau emerged as an adversary of the colonial government when, in October 1866, he accompanied about 100 Ngāti Hineuru under Te Rangihīroa to Ōmarunui 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 Rangitāhau and others were deported to Wharekauri (Chatham Island).
In July 1868 Te Rangitāhau 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 Pāparatū, Te Kōneke 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 Pākehā settlers and Māori on the East Coast. Te Rangitāhau was one of the leaders of the attack on Major Reginald Biggs's house during the raid on Matawhero on 10 November 1868.
Te Rangitāhau withdrew into Urewera with Te Kooti following their escape from the siege of Ngātapa in January 1869. He re-emerged on 9 March along with a rebuilt force under Ngāti Tūwharetoa chief Wirihana Koikoi, who led the attack on Ngāti Pūkeko near Whakatāne. He was also one of the leaders of a raiding party sent to Uretara Island near Ōhiwa where Robert Pitcairn, a surveyor, was killed. After further skirmishing the force travelled to Hawke's Bay and attacked Ngāti Pāhauwera of Mōhaka on 10 April 1869, taking the lives of at least 57 Māori and seven Pākehā. Te Rangitāhau 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 Rangitāiki plains, east of Taupō. A new campaign began in this area. Te Rangitāhau helped to guide Te Kooti's forces to Lake Taupō and led an advance party during the brilliantly executed stratagem which, at Ōpepe 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 Ngāti Tūwharetoa territory. It unsettled the government and its Māori 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 Ngāti Tūwharetoa for their support of the government. He would then cement an alliance with the sympathetic southern Ngāti Tūwharetoa hapu, gain King movement support and defeat the government forces in battle. This plan brought about the defection of Te Rangitāhau for reasons that remain unclear. According to one version of events, he protested at Te Kooti's intention because the northern Ngāti Tūwharetoa 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 Rangitāhau was to do the killing, but when they were in Ngāti Tūwharetoa territory, Te Kooti was to have the responsibility. When they reached the Taupō area, Te Rangitāhau did not honour the agreement; instead, he warned his people between Waipāhīhī and Kōrohe (and possibly those of Tapuaeharuru) to flee. As a consequence of the betrayal Te Kooti and Te Rangitāhau may actually have fought each other.
It is probable that Te Rangitāhau took no part in Te Kooti's final stand at Te Pōrere on 4 October 1869. He may have returned to Ōpepe, 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 Rangitāhau and 30 men sought refuge at Ōhinemuri 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 Rangitāhau's absence from the Taupō campaigns made Te Kooti's military objectives more difficult to achieve. He had been, in a sense, Te Kooti's passport through the Taupō 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 Ngāti Tūwharetoa remaining with Te Kooti were those with Horonuku Te Heuheu, who may not have been strongly committed to Te Kooti's cause.
Te Rangitāhau 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 Māori 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 Rangitāhau's mana and power, which may have ensured a degree of autonomy for him within Ngāti Tūwharetoa 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 Rangitāhau was living at Taupō 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 Pāoro, and that his widow, whose name is unknown, was living at Waitahanui about 1910. In 1900, Te Rangitāhau visited Rotorua to perform a tapu-raising ceremony on a carved house. The Ngāti Awa tohunga, Hāmiora Tumutara Pio, also took part in the ceremonies. It is said that their rival powers were so great that Te Rangitāhau died a few days after the ceremony, and Pio shortly thereafter.