Te Rauparaha was the son of Werawera, of Ngati Toa, and his second wife, Parekowhatu (Parekohatu), of Ngati Raukawa. He is said to have been a boy when Captain James Cook was in New Zealand. If so, it is likely that he was born in the 1760s. He was born either at Kawhia or at his mother's home, Maungatautari. He was descended from Hoturoa of the Tainui canoe; both his parents were descended from the founding ancestors of their tribes. Although not of the highest rank, he rose to the leadership of Ngati Toa because of his aggressive defence of his tribe's interests and his skill in battle. He was short in stature but of great muscular strength. In profile, he had aquiline features; when excited his eyes would gleam and his lower lip would curl downwards.

His name is derived from an edible plant called rauparaha. Soon after he was born a Waikato warrior who had killed and eaten a relation of his threatened to eat the child as well, roasted with rauparaha leaves; the child was called Te Rauparaha in defiance of this threat. The other name by which he was known during his childhood was Maui Potiki, because he, like Maui Potiki, was lively and mischievous. Much of his childhood was spent with his mother's people at Maungatautari, but he may have been instructed at the whare wananga at Kawhia.

From the late eighteenth century Ngati Toa and related tribes, including Ngati Raukawa, were constantly at war with the Waikato tribes for control of the rich fertile land north of Kawhia. The wars intensified whenever a major chief was killed or insults and slights suffered. Te Rauparaha was involved in many of these incidents as tensions mounted. He led a war party into disputed territory north of Kawhia and the Waikato chief Te Uira was killed. On another occasion he led a war party by canoe to Whaingaroa (Raglan Harbour) to avenge the killing of a group of Ngati Toa; his nieces had been among the victims. Young warriors gathered around him as he was an aggressive war leader.

As warfare intensified Ngati Toa killed Te Aho-o-te-rangi, a Waikato chief, who had led an attack on Kawhia. Te Rau-anga-anga, Te Aho-o-te-rangi's grandson and father of Te Wherowhero, led a large war party to avenge his killing. Ngati Toa were driven back to the pa of Te Totara, at the southern end of Kawhia Harbour, where peace was made, but it was broken when Te Rauparaha led a fishing party into grounds claimed by Ngati Maniapoto. Waikato came to the assistance of Ngati Maniapoto and took the pa of Hikuparoa after a feigned retreat. Te Rauparaha escaped to Te Totara pa and after much fighting peace was restored.

Te Rauparaha left Kawhia after this episode but on his return joined a war party seeking revenge for the death of a prominent Ngati Toa warrior, Tarapeke, in a duel outside Te Totara. Under Te Rauparaha's command they went north and killed Te Wharengori of Ngati Pou. Waikato again invaded Kawhia, and after defeat in several battles Ngati Toa retreated to Ohaua-te-rangi pa. However, there were relations of Waitohi, Te Rauparaha's sister, among the attackers, and through them she negotiated a peaceful settlement.

During times of peace Te Rauparaha travelled widely to visit tribes friendly to Ngati Toa. He was at Maungatautari when Ngati Raukawa chief Hape-ki-tu-a-rangi died and he became his successor by responding to the chief's dying query, 'Who will take my place?' None of Hape's sons or relatives responded. Te Rauparaha later took Hape's widow, Te Akau, as his fifth wife. He had previously married Marore, Kahuirangi, Rangi-ta-moana (the sister of Marore), and Hopenui. Between 1810 and 1815 Te Rauparaha was with Ngati Maru in the Hauraki Gulf and was given his first musket. He also visited Ngati Whatua at Kaipara, where he was probably trying to build a coalition to attack Waikato. It is possible, too, that he was looking for a place where his tribe could be resettled.

Ngati Toa had long-standing alliances with the tribes of northern Taranaki, the southern neighbours of Ngati Maniapoto. In 1816 the marriage festivities of Nohorua, Te Rauparaha's older half-brother, and a woman of Ngati Rahiri, turned to disaster when the canoes of Ngati Rahiri carrying a return feast overturned. In fury Ngati Rahiri attacked Ngati Toa. Two Ngati Whatua chiefs, Murupaenga and Tuwhare, from north of present day Auckland, joined Ngati Toa's retaliatory raid into Taranaki about 1818. However, Ngati Rahiri were old allies and peace was made at Te Taniwha pa. As part of the peacemaking, muskets were fired for the first time in Taranaki. Later, Te Rauparaha joined Te Puoho-o-te-rangi of Ngati Tama in attacks on other Taranaki tribes, before returning to Kawhia.

In 1819 Te Rauparaha joined a large northern war party, armed with muskets, led by Tuwhare, Patuone and Nene. This expedition passed through the lands of Te Ati Awa, Ngati Toa's allies, and attacked Ngati Maru-whara-nui of central Taranaki. Te Kerikeringa and other pa fell to them; warriors who had never encountered guns before became demoralised. In this manner the expedition continued south to Cook Strait. Ngati Ira successfully held a pa at Pukerua with traditional weapons but were deceived by a false offer of peace, it is said from Te Rauparaha. On its return the expedition fought with Ngati Apa in Rangitikei. Te Rangihaeata, Te Rauparaha's nephew, captured Te Pikinga of Ngati Apa and made her his wife. On reaching Kawhia Nga Puhi gave muskets to Ngati Toa and continued on their way north.

Te Rauparaha probably also took part in the expedition of 1819–20 to find a new home for his people. Their position at Kawhia was becoming untenable as war with the Waikato tribes intensified. While at Cook Strait Te Rauparaha had seen a sailing ship passing through the strait, probably one of the Russian ships of the Bellingshausen expedition. A northern chief told him that there were good people on the ships, and that if he moved south he could become great by trading for guns with the ships now coming to Cook Strait.

About this time Te Rauparaha's wife Marore was killed in Waikato while attending a funeral. In revenge he and her relations killed a Waikato chief on a pathway where travellers had safe conduct. In 1820 several thousand Waikato and Ngati Maniapoto warriors invaded Kawhia. Ngati Toa was defeated at Te Kakara, near Lake Taharoa, and Waikawau pa, south of Tirau Point, was captured. Te Rauparaha withdrew to Te Arawi pa, near Kawhia Harbour, which was besieged. Among the besiegers were relations of Ngati Toa who did not wish to see the tribe exterminated. Ngati Maniapoto leader Te Rangi-tua-taka secretly supplied food to the pa and advised Te Rauparaha to take refuge with Te Ati Awa in Taranaki. Te Rauparaha had considered fleeing east to his Ngati Raukawa relations, but the way was blocked by hostile forces. Because many were closely related to Waikato tribes they were allowed to leave Kawhia and begin the first section of their migration to the south, known as Te Heke Tahu-tahu-ahi.

Te Rauparaha burned his carved house and recited a lament for Kawhia. Ngati Toa went a few miles south to Pukeroa pa, where the people were related to both Ngati Toa and Ngati Maniapoto. Most women and children and the injured were left there while the warriors went further south and crossed the Mokau River into the territory of their Ngati Tama allies. Te Rauparaha went back to Pukeroa with 20 warriors armed with muskets to bring out those left behind. He knew that Ngati Maniapoto had come in pursuit so he dressed his people in red cloth and spread a rumour that a Nga Puhi war party, wearing red, was in the area. Ngati Maniapoto then kept away from the refugees. At night, while waiting to cross the Mokau River, Te Rauparaha addressed imaginary groups of warriors, lit many fires and spread cloaks over bushes, to give the impression of a large army. Reunited south of the Mokau, about 1,500 Ngati Toa went to Te Kaweka in Taranaki and began cultivating land Te Ati Awa allowed them to use. A Waikato force, led by Te Wherowhero, came south but was defeated at the battle of Motunui in late 1821 or early 1822. It is said that after this battle Te Rauparaha in his turn helped Waikato by warning them not to retreat north, where a Ngati Tama force was waiting. This victory freed Ngati Toa from the threat of pursuit.

Te Rauparaha left Ngati Toa in Taranaki and returned north to Maungatautari, to try to persuade Ngati Raukawa to join his migration because he needed more fighting men. But Ngati Raukawa had other ambitions in Heretaunga (Hawke's Bay). He then went on to Rotorua and encouraged Te Arawa to attack a Nga Puhi war party, to avenge the killing by Nga Puhi of his Ngati Maru relations. Some Tuhourangi had joined the attack on Nga Puhi, and followed Te Rauparaha back to Taranaki.

By 1822 the section of the migration of Ngati Toa known as Te Heke Tataramoa, which was to bring them to Kapiti Island, was under way. Joined by some Te Ati Awa, the migration travelled 250 miles through enemy land which Te Rauparaha had raided several years before. The migration was initially peaceful because Te Rauparaha had made peace and marriage alliances with some tribes. Others retreated from his path, having learned to fear a war party armed with muskets, and distrusting his intentions. The Wanganui tribes withdrew upriver, and in Rangitikei Ngati Apa were at first friendly; they were related to Ngati Toa by the marriage of Te Pikinga to Te Rangihaeata.

Trouble began when the migration reached the Manawatu River. Canoes were stolen when Nohorua led a foraging expedition. In revenge Ngati Toa attacked a Rangitane settlement and killed several people. The tribes of Manawatu and Horowhenua began to resist. Toheriri of Muaupoko invited Te Rauparaha and his family to a feast near Lake Papa-i-tonga; when night fell Muaupoko began killing them. Te Rauparaha escaped but his son Te Rangi-hounga-riri and daughter Te Uira, and at least one other of his children, were killed. He vowed to kill Muaupoko from dawn until dusk. The lake pa of Muaupoko were taken and they were massacred without mercy.

While Te Rauparaha was attacking the tribes of Horowhenua, Te Pehi Kupe, the senior chief of Ngati Toa, surprised Muaupoko on Kapiti and captured the island. As Ngati Toa were threatened by both Ngati Kahungunu and Ngati Apa, they moved to Kapiti for security. Fighting continued on the mainland. Rangitane were slaughtered at Hotuiti, after a false offer of peace had disarmed them. A great canoe fleet of southern tribes assembled about 1824, with contingents from Taranaki to Te Whanganui-a-Tara (Wellington Harbour) in the North Island and from the South Island. A night attack made on Kapiti at Waiorua was defeated. This victory established Ngati Toa securely in the south of the North Island. Allies from Taranaki and from Ngati Raukawa joined Te Rauparaha in numerous migrations over the next decade and were found land in the conquered territories.

Whalers and other European ships had been trading at Kapiti since 1827. Te Rauparaha's power over his allied tribes rested on his control of the trade in arms and ammunition. Captives were taken to Kapiti to scrape flax to be traded for muskets, powder and tobacco. He also wanted to control the supply of greenstone, and the South Island, where greenstone was to be found, was open to conquest as the tribes there had not yet acquired guns. Some of their chiefs had insulted him and some had fought against Ngati Toa at Waiorua. About 1827 Te Rauparaha took a war party across Cook Strait to Wairau, where several Rangitane pa were taken. A year or so later a larger invasion fleet left Kapiti. Te Ati Awa attacked the territory around Te Ara-a-Paoa (Queen Charlotte Sound), while Te Rauparaha, with 340 warriors mostly armed with guns, entered Te Hoiere (Pelorus Sound) and heavily defeated Ngati Kuia at Hikapu. At Kaikoura many Ngai Tahu were taken by surprise and killed or enslaved.

Te Rauparaha led part of the war party to the Ngai Tahu stronghold, Kaiapoi pa. Te Pehi Kupe and seven other Ngati Toa chiefs entered the pa to trade for greenstone. The people at Kaiapoi knew of the attack on their relations at Kaikoura and the Ngati Toa chiefs were killed and eaten. Ngati Toa then unsuccessfully attacked the pa, although killing about 100 Ngai Tahu prisoners. Te Rauparaha returned to Kapiti. In 1830 the attack on Ngai Tahu was resumed. Captain John Stewart took about 100 Ngati Toa warriors to Akaroa, hidden in the brig Elizabeth. He lured Ngai Tahu chief Tama-i-hara-nui aboard by offering to trade for muskets. Tama-i-hara-nui was taken, together with his wife and daughter, tortured and put to death at Kapiti. On the ship, he strangled his daughter to prevent her from being enslaved.

Te Rauparaha went to Sydney in 1830 where he met Samuel Marsden, the chaplain of New South Wales. The ship that returned him to Kapiti is said to have taken him and his warriors to Rangitoto (D'Urville Island), where they captured Ngati Kuia refugees, and to have transported them to Kapiti. In 1831 Te Rauparaha again besieged Kaiapoi pa and captured the pa by sapping and by firing the palisades. He returned to Akaroa and took the pa Onawe, and then returned to Kapiti, leaving his allies and some of his own people to rule over the enslaved tribes. Meanwhile the migrant tribes in the south-west of the North Island, none of which accepted Te Rauparaha's authority, were competing with each other and with the original inhabitants for land and resources. Fighting broke out between Ngati Raukawa and Te Ati Awa in 1834; this threatened Te Rauparaha's leadership, as he was allied to Ngati Raukawa. Other Ngati Toa, led by Te Hiko-o-te-rangi, the son of Te Pehi Kupe, supported Te Ati Awa and besieged Te Rauparaha at the Rangiuru Stream. He had to appeal to the Ngati Tuwharetoa leader Mananui Te Heuheu Tukino II for help. When peace was made Te Rauparaha at first intended to return to the north with Mananui. But he was persuaded to stay by Te Rangihaeata and went back to Kapiti. By the mid 1830s Te Rauparaha and his allies had conquered the south-west of the North Island and most of the northern half of the South Island.

He now wanted to extend his conquest to the rest of the South Island; however, Ngai Tahu had obtained guns from the whalers in Otago and were able to resist him. About 1833 he had been nearly captured by Ngai Tahu from Otago, at Kapara-te-hau (Lake Grassmere). Inconclusive battles were fought at Oraumoa-iti and Oraumoa-nui. Te Rauparaha was unable to prevent Ngai Tahu attacks on whaling stations under his patronage and when they sent a war party to the Cook Strait area in the late 1830s he did not confront it.

After Te Rauparaha's sister, Waitohi, the mother of Te Rangihaeata, died in 1839 war broke out among the tribes allied to Te Rauparaha. A huge funeral gathering was held. A Rangitane slave of Te Ati Awa, who had brought tribute from the South Island, was killed and eaten, against Te Ati Awa's wishes. Quarrelling at the feast led to renewed fighting between Te Ati Awa and Ngati Raukawa, culminating in the battle of Te Kuititanga at Waikanae. Te Rauparaha crossed over from Kapiti to assist Ngati Raukawa, but had to escape in a whaling boat when they suffered a severe defeat. After the battle there was no looting of the dead or cannibalism, as Christian influences had been brought to Te Ati Awa by freed slaves returning from the Bay of Islands. Ngati Raukawa dead were buried with their clothing and arms and ammunition.

Later in the same day as the battle of Te Kuititanga, 16 October 1839, the New Zealand Company ship Tory arrived at Kapiti. Colonel William Wakefield wanted to buy vast tracts of land. Negotiations took place and Te Rauparaha accepted guns, blankets and other goods for the sale of land, the extent of which later became a matter of dispute. He insisted that he had only sold Whakatu and Te Taitapu, in the Nelson and Golden Bay areas. All land sales were declared void by Lieutenant Governor William Hobson after his arrival in 1840, and a commission was set up to investigate land claims. On 14 May 1840 Te Rauparaha signed a copy of the Treaty of Waitangi presented to him by CMS missionary Henry Williams. He believed that the treaty would guarantee him and his allies the possession of territories gained by conquest over the previous 18 years. He signed another copy of the treaty on 19 June, when Major Thomas Bunbury insisted that he do so.

Te Rauparaha resisted European settlement in those areas he claimed he had not sold. Disputes occurred over Porirua and the Hutt Valley. But the major clash came in 1843 when Te Rauparaha and Te Rangihaeata prevented the survey of the Wairau plains. Arthur Wakefield led a party of armed settlers from Nelson to try to arrest Te Rauparaha. Fighting broke out in which Te Rongo, the wife of Te Rangihaeata, was killed. After the settlers had surrendered, Te Rangihaeata killed them to avenge his wife's death.

In the crisis that followed Te Rauparaha stayed on the defensive. There was a reluctance for war among those influenced by the missionary Octavius Hadfield at Otaki. Te Rauparaha had much to lose if he attacked the European settlements. Settlers believed that he intended war and that he had sent for a Wanganui war party to attack Wellington, as Te Ati Awa of Waikanae had refused to do so. The crisis was ended on 12 February 1844 when Governor Robert FitzRoy declared at Waikanae that the settlers had provoked the fighting at Wairau and that although he deplored the killing of the prisoners no further action would be taken. During this crisis Te Rauparaha, by avoiding war with the settlers, contributed greatly to its peaceful resolution.

On 16 May 1846 Te Mamaku, of Wanganui, who had joined Te Rangihaeata in resisting settlement, led an attack on the troops stationed at Almon Boulcott's farm in the Hutt Valley. There were again rumours of an imminent assault on Wellington. The new governor, George Grey, decided that Te Rauparaha could not be trusted and must be arrested. He visited him at his Taupo pa, near Porirua, and then left on the naval vessel Driver. Two hours before dawn the ship returned and British troops took Te Rauparaha on board. He was held without charge on another naval vessel, the Calliope, for 10 months and then allowed to live in Auckland. On his petition to the governor he was returned to his people at Otaki in 1848. He was accompanied on the return voyage by George and Eliza Grey, and by numerous Maori, including Potatau Te Wherowhero.

Te Rauparaha lived at Otaki for the brief remainder of his life, although he visited Wairau. By the end of his life his influence appears to have declined, possibly because of the humiliation of his imprisonment. His wives in the last part of his life were Pipikutia, Kahukino and Kahutaiki. He had had 8 wives in the course of his life, and 14 children, some of whom survived him. He did not adopt Christianity, although he attended church services. Te Rauparaha died on 27 November 1849 and was buried near the church, Rangiatea, in Otaki. He is believed to have been reinterred on Kapiti.

Te Rauparaha was a great tribal leader. He took his tribe from defeat at Kawhia to the conquest of new territories in central New Zealand. As a war leader he enjoyed great success. The tribes he defeated attribute his success to Ngati Toa's possession of muskets rather than to Te Rauparaha's military genius. Without his leadership, however, it is doubtful if Ngati Toa would have attempted the great migration and seized the opportunities open to them. Having done so, they changed the tribal structure of New Zealand for ever.