Hirini Te Rito Whaanga was born on Māhia Peninsula, according to most sources in 1828, the eldest son of Īhaka Whaanga, a prominent Ngāti Rākaipaaka and Ngāti Kahungunu leader, and his wife, Te Haka Rākātō. He was trained in the whare wānanga at Waikawa (Portland Island) and worked in the whaling trade. According to family tradition he married three times. His first wife was Katirina Apatū, who is said to have died in 1850; they had a daughter, Te Rina. Rīpeka Pōmare, his second wife, was a high-born Māhia woman with whom he had two children, Raiha and Ereti, before her death in 1863. His third wife, Mere Mete, was the daughter of the Māhia whaler Hachem Schmidt, also known as John Smith. Their children were Mihi Mere, Katarina, and two who died as children, Īhaka and Heneriata.
Hirini Whaanga farmed the tribe's land on Māhia Peninsula with some success. His father was a patron of the European presence on the East Coast and a leader of pro-government Māori during the wars of the 1860s. Hirini accompanied his father on some military campaigns. The family were loyal Anglicans strongly opposed to the Pai Mārire religion and its Hauhau following. However, in the disenchantment which followed the wars, Anglicanism – associated with the government – was much criticised by local Māori. In August and September 1884 three American missionaries of the Church of Jesus Christ of Latter-day Saints (or Mormon faith) arrived in Nūhaka as part of an evangelistic tour of the east coast. Some 210 adults, a high proportion of the Anglican community on Māhia Peninsula, were converted. Hirini Whaanga was the most prominent convert among the Māori people. He was baptised at Nūhaka on 30 November 1884 by the missionary John C. Stewart. He won the respect of the young missionaries, for whom he provided gifts and hospitality, and he was a popular speaker at Mormon conferences.
In 1894 Hirini Whaanga, feeling an obligation as leader to ensure the salvation of his people, determined to join the stream of migrants from all over the world to 'Zion' by carrying out spiritual rites at the Mormon temples in Utah. His young relation, Pirika Whaanga, had been adopted and taken to Salt Lake City in 1886, and although Whaanga spoke no English he laboured to raise sufficient money to make the same journey. On 14 January 1894 the missionaries ordained him a priest in the Aaronic order, and in June 1894 he departed on the Monowai. He was accompanied by his wife, Mere Whaanga; his daughter Mihi Mere's son, Hirini (Sid) Christy; his wife's nephew Wātene Smith; an adopted daughter, Ena Pōmare; his sister-in-law, Apikara; and her sons Īhāia and Īhaka. Three returning American elders, William Douglass, Lars Christian Rasmussen and William Wesley Gibson, also travelled with them. Meanwhile the family home in Nūhaka became a missionary residence.
The First Presidency of the Latter-day Saints church, consisting of the president assisted by two counsellors, had discouraged 'native converts' from coming to Salt Lake City, and initially Whaanga was thought to have brought two wives, at a time when polygamy was jeopardising the acceptance of Mormons within the United States. He was placed in the care of the former missionary John C. Stewart at Kanab, in southern Utah, who persuaded him to invest his money on projects which benefited Stewart but reduced Whaanga to desperate financial straits. Zion's Māori Association, a body of ex-missionaries to New Zealand, rescued him and took him to Salt Lake City, providing the family with a home.
There was some nervousness among Mormon Māori in New Zealand when Hirini Whaanga did not return within a year or two, particularly as other Māori were discouraged from going to America. However, in 1898, at the age of 69 or 70, he was called by the First Presidency to undertake a mission to New Zealand. He did so enthusiastically, hoping to gather genealogies for his temple work. While in New Zealand he evangelised many Māori communities, travelling in the company of the American Ezra T. Stevenson, who had been called to serve as president of the New Zealand mission. Whaanga made a particularly strong impact at Māhia.
In April 1899 his tour was cut short and he returned to Utah. Hirini Whaanga lived there until his death on 17 October 1905. Mere Whaanga returned to New Zealand twice after his death, but could not settle and went back to Utah. A picture of Hirini Te Rito Whaanga was unveiled at a Mormon festival in Nūhaka at Easter 1941, and he remains a deeply respected figure among Mormon Māori in New Zealand.