Kīngi Tāwhiao (Tūkaroto Matutaera Pōtatau Te Wherowhero Tāwhiao, Māori: [taːɸiao tʉːkaɾɔtɔ matʉtaeɾa pɔːtatau tɛ ɸɛɾɔɸɛɾɔ]; c. 1822 – 26 August 1894), known initially as Matutaera, reigned as the Māori King from 1860 until his death. After his flight to the King Country, Tāwhiao was also Paramount Chief of Te Rohe Pōtae for 17 years, until 1881. A rangatira, and a religious figure – a tohunga ariki – Tāwhiao amassed power and authority during a time of momentous change, to become de facto leader of the Waikato tribes. He was a member of the Ngati Mahuta hapū and the kāhui ariki, the Kīngitanga royal family.

The son of kīngi Pōtatau te Wherowhero, Tāwhiao was elected the second Māori King after his father's death in 1860. Unlike his unenthusiastic father, Tāwhiao embraced the kingship, and responded immediately to the challenge of ongoing Raukawa and Tainui support for Te Āti Awa during the First Taranaki War. In 1863, Tāwhiao was baptised into the Pai Mārire faith, taking his regnal name, before leading the response to the invasion of the Waikato. After the Kīngitanga suffered a heavy defeat at the Battle of Rangiriri and war crimes at the trading centre of Rangiaowhia, Tāwhiao led the exodus of Tainui to the land of Ngāti Maniapoto, establishing a secessionist state called Te Rohe Pōtae (the King Country). Warning all Europeans that they risked death if they crossed the border, he governed Te Rohe Pōtae as an independent state for almost twenty years. Tāwhiao's power began to decline significantly in the 1880s, as his relations with Raukawa ki Ngāti Maniapoto deteriorated. He formally sued for peace with George Grey at Pirongia on 11 July 1881, allowing the construction of the North Island Main Trunk railway line, which first opened the King Country up to the outside world. Attempts by Tāwhiao to regain personal sovereignty or establish co-governance in accordance with the Treaty of Waitangi failed, and the Kīngitanga began to lose its supporters. The king died suddenly in August 1894, and was succeeded by his son Mahuta Tāwhiao.

Tāwhiao's legacy includes building the kingitanga from a union of mid-Northern tribes into "one of New Zealand’s most enduring political institutions," becoming a powerful adversary of the Crown that endured even after the exodus into the King Country and the eventual loss of its sovereignty. He is credited with establishing several key Kīngitanga institutions, including Te Whakakitenga, the bicameral legislature of Waikato Tainui, and the annual Poukai conference, as well as the initial Kīngitanga Bank, which collapsed, and then the successful Bank of Aotearoa. Tāwhiao has also been the subject of controversy, in connection with the forfeiture of the Kīngitanga Bank, and his conversion to Mormonism.

Tūkaroto Pōtatau Te Wherowhero (Tainui orthonography: Tuukaroto Pootatau Te Wherowhero) was born around 1822 at Ngāruawāhia. His father, Te Wherowhero, was arguably the Paramount Chief of the Waikato people, and his mother, Whakaawi, was Te Wherowhero's senior wife. Te Wherowhero the younger was raised through whāngai by his mother's parents, making him distant from his father. He was named Tūkāroto in commemoration of his father's stand at the siege of Mātakitaki pā in May 1822 against Ngāpuhi. After the Waikato were defeated by musket-armed Ngāpuhi led by Hongi Hika in a battle at Matakitaki (Pirongia) in 1822, they retreated to Orongokoekoea Pā, in what is now the King Country, and lived there for several years. Tāwhiao was born at Orongokoekoea in about 1825 and was named Tūkaroto to commemorate, it is said, his father's stand at Matakitaki.

Tāwhiao's name changed throughout his life. Initially known as Tūkaroto, he was later baptised Matutaera (Methuselah) by Anglican missionary Robert Burrows, a name he would repudiate in 1867. Te Ua Haumēne, the Hauhau prophet and founder of the Pai Mārire faith, sought counsel with the king in the 1860s. After the invasion of the Waikato in 1863, Matutaera travelled to Te Namu pā in Ōpunake to meet him. There, Matutaera was baptised into the Pai Mārire faith, taking the name Tāwhiao, meaning "encircle the world".

In 1858 Tāwhiao's father, Pōtatau Te Wherowhero, was installed as the first Māori King (taking the name Pōtatau), his purpose being to promote unity among the Māori people in the face of Pākehā encroachment. Pōtatau was an unwilling ruler, and acquiesced to accept the crown as merely a transitional holder. Several rūnanga were held to discuss the proposal for the elderly Te Wherowhero to ascend to the Kingitanga. One such hui was an 1857 meeting known as Te Puna o te Roimata (the wellspring of tears), at Haurua, south of Ōtorohanga, hosted by Tainui kin Ngāti Maniapoto. Tanirau, a powerful Ngāti Maniapoto chief, announced the iwi's at-large decision to support Pōtatau as king. Pōtatau replied, ‘E Tā, kua tō te rā’ (O sir, the sun is about to set), a proverb commenting on his advanced age and poor health, implying he had not much longer to live. Tanirau replied, ‘E tō ana i te ahiahi, e ara ana i te ata, e tū koe he Kīngi’ (it sets in the evening to rise again in the morning; thou art raised up a king). This referred to the possibility of introducing hereditary rule to the monarchy; Tanirau later espoused support for Tāwhiao (then known as Matutaera) or his siblings to succeed Pōtatau Te Wherowhero upon the latter's death. Pōtatau replied, ‘E pai ana’ (it is good), and ascended to the kingship, and to Waikato the role of kaitiaki of the Kīngitanga. The Kīngitanga remains a hereditary monarchy, and is yet to leave the hands of Waikato Tainui.

When Pōtatau died in 1860, Tāwhiao, his sister Te Paea Tiaho, and Wiremu Tamihana Tarapipipi of Ngāti Hauā were candidates to succeed him. Tāwhiao was chosen and reigned for thirty-four years during one of the most difficult and discouraging periods of Māori history. During this period there were two governments de jure; English law and governance prevailed within the British settlements and Māori custom over the rest of the country, although the influence of the King was largely confined to the Waikato and even there chiefs such as Rewi Maniapoto only cooperated with the king when it suited them. However the Pākehā population was increasing rapidly while the Māori population was unknown as there was no reliable census of Maori and Pākehā / Maori for 80 years. Because Maori separated themselves from Pākehā, many believed, wrongly, that the Maori population was declining rapidly. This was also the period when British industrial, trade and political power was at its height. The presence of an independent native state in the central North Island was officially ignored by the government until it developed the potential to undermine the colonial government's sovereignty.

After Tāwhiao converted to the Pai Mārire faith in early 1863, he and Te Ua Haumene established Te Kīwai o te Kete, the military pact forged between Taranaki and Tainui Māori during the New Zealand Wars. The two iwi had recently allied in 1860, during the First Taranaki War, when Kingitanga forces under the command of Epiha Tokohihi had come to the aid of Taranaki leader Wiremu Kīngi Te Rangitāke. Pōtatau Te Wherowhero had died in June 1860, making the First Taranaki War Tāwhiao's first major challenge. Tāwhiao supported the Kīngitanga's uniting principle of opposition to the sale of Māori land, to prevent the spread of British sovereignty, but as a pacifist he was divided over how to respond. Both Wiremu Kīngi and the Colonial Government had made repeated diplomatic approaches to Pōtatau to ask him for military and diplomatic support, but by early May Pōtatau seemed to have decided to offer at least token support to Taranaki Māori, sending a Kingite war party to the district under the control of war chief Epiha Tokohihi. Tāwhiao eventually opted to maintain this policy.