Hukunui Manaia was a leader of Ngāti Tū hapū of Ngāti Ruanui, whose territory was the coastal section of the Waimate Plain, in South Taranaki, between the Īnaha and Ōtakeho streams. Neither the names of his parents nor his date of birth are known.
Manaia first came to prominence during the Waikato invasions of Taranaki in the 1820s and 1830s, when he led his people to refuge on Mt Taranaki. In May 1834 he was among the plunderers of the wreck of the Harriet near Cape Egmont. He later told how the Māori were mystified by the unfamiliar foodstuffs and other provisions; they thought flour was sand and tried to cook soap which they thought was food.
In 1836 Manaia joined Te Matakātea in Waimate pā, at the mouth of the Kapuni Stream, where a final Waikato invasion was repulsed. His descendants say he took no part in the fighting, being a man of peace, but Te Kāhui credited him with shooting some of the attackers from a tower.
Once peace returned, Manaia settled at Te Kauae pā. Although his name Wiremu suggests he was baptised, missionary accounts do not mention him. He took no part in the fighting in the 1860s, and in 1866 he joined Hōne Pīhama in submitting to the government. Arthur Atkinson met him at Te Kauae in February 1867 and found him 'very hospitable'.
Manaia tried to keep the peace during Tītokowaru's War in 1868–69, making an unsuccessful attempt to recover horses taken by Tītokowaru's men from Lieutenant Colonel Thomas McDonnell's troops at Camp Waihī. After Tītokowaru's campaign Manaia met Civil Commissioner Robert Parris in October 1869 and co-operated in the construction of the coach road across the Waimate Plain. His crop of potatoes and grass seed made him independent and he declined to accept takoha (gifts) from Major Charles Brown, the civil commissioner, to assist in fencing reserves and 'social improvement'.
Manaia's pacific nature was again in evidence during the conflict over the settlement of the Waimate Plain in the early 1880s. The surveyor Harry M. Skeet worked under Manaia's protection, naming the township of Manaia in his honour. Manaia tried to reassure the settlers that they had nothing to fear from Te Whiti-o-Rongomai III, leader of the Māori resistance to attempts at surveying the district. When the Māori township of Parihaka was dispersed by government troops in November 1881, Manaia killed eight bullocks and provided other food for its people. He was also able to assist Tītokowaru by standing bail for him in July 1882.
Manaia declined to give evidence on his land claims to the west coast commissioners in 1880, preferring that Robert Parris speak for him. In 1882 and 1883 Crown grants for 5,944 acres at Kaūpokonui were issued to him and Ngāti Tū. In 1887 the house named Parakau was built at Waiōkura in his honour.
Manaia was described as a spare, tall man of stately carriage whose face had been tattooed in his youth. He died in 1892 leaving no direct descendants. He had three brothers, Kato Ruka, Ngātairākaunui and Ngonge Ngonge, and it is from the latter two that present descendants derive.