Gilbert Mair is said to have been born at Whāngārei, New Zealand, on 10 January 1843, the eighth of twelve children of Elizabeth Gilbert Puckey and her husband, Gilbert Mair, a merchant trader. Gilbert Mair senior was born at Peterhead, Aberdeenshire, Scotland, in 1799, the son of a shipowner. Arriving in the Bay of Islands in 1824, he helped Henry Williams build the schooner Herald, which he later commanded in mission service until it was wrecked on the Hokianga bar. After his marriage in Sydney, New South Wales, in September 1827, Mair obtained land in Te Wahapū Inlet, in the Bay of Islands, where he built up a flourishing trading station. One of the first to exploit the kauri gum industry, he exported gum to the United States and timber and flax to Sydney. Mair was involved in representations to the British government to have New Zealand declared a British colony, and in the formation of the Kororāreka Association, a controversial attempt at settler self-rule. In 1842 he disposed of his trading station and other interests and moved his family to Whāngārei, where he had acquired land. He died at Kaipara on 16 July 1857.
Gilbert Mair the younger grew up on the family farm at Whāngārei, which was called Deveron after the Mair home in Scotland. Shortly after his birth he was given the name Tawatawhiti by local Māori; he was later known to all his friends as Tawa. Small boned, wiry and athletic, he became a keen sportsman and accomplished horseman. While assisting his father in his kauri gum export business, he came into close contact with many Te Arawa who had moved north from the Rotorua district to dig in the gumfields. He learned to speak Māori fluently and developed an enduring interest in Māori history and culture.
Articled to the surveyor general in Auckland in 1860, Mair gained a provincial surveyor's certificate in 1864. He was clerk of the court and interpreter at the Resident Magistrate's Court in Tauranga when a boundary dispute erupted into fighting in January 1867. The Pirirākau hapū, Pai Mārire adherents who had refused to participate in the surrender to the government in 1864, resisted confiscation within their tribal boundaries. Their protest was misinterpreted as a deliberate act of provocation, and military settlers' fears of an attack on Tauranga were roused. Mair volunteered for active service in the militia and was attached to the 1st Regiment of the Waikato Militia. He took part in a series of expeditions mounted by the militia, with the assistance of volunteers and Te Arawa auxiliary forces under the command of his brother, William Mair, to disperse the 'rebels' and their allies. In his first action Mair was mentioned in dispatches for rescuing a soldier under heavy fire, and he was later promoted to ensign after leading an attack on the rifle pits at Taumata, south of Tauranga.
In a lone scouting expedition, which he initiated, Mair was able to confirm that a force of Waikato and Ngāti Hauā sought revenge on Te Arawa by raiding Rotorua. He was dispatched with a small force of Te Arawa to reinforce the Rotorua people and on 17 March 1867, with his men, forced the attackers to retreat after fierce skirmishing at Te Koutu pā. After the arrival of militia reinforcements, an assault was launched on Puraku pā, overlooking the Rotorua basin, which had been occupied and fortified by Waikato under Kihitu. Mair, with 100 Te Arawa, attempted to cut off the retreat from the rear of the pā. For his part in the actions at Te Koutu and Puraku Mair was promoted to lieutenant on 25 April 1867.
In January 1868 Mair accompanied the under secretary for native affairs, William Rolleston, to the Chatham Islands, where Māori prisoners were detained. Mair found conditions and the treatment of prisoners so unsatisfactory that he declined an appointment to take command of the garrison. At Wharekauri on the Chathams Mair had his first encounter with religious leader and prophet Te Kooti Arikirangi. His second encounter followed a lightning raid by Te Kooti on the Whakatāne valley in March 1869, to obtain ammunition and to secure new recruits. Confronted by a defence force of militia and kūpapa hastily organised by the Mair brothers, Te Kooti retreated first to Tauaroa pā in the Rangitāiki valley, and then into the Urewera.
In May 1869 the government mounted a three-pronged invasion of the Urewera, to crush Te Kooti's resistance. Mair was placed in charge of a force of Te Arawa attached to Colonel G. S. Whitmore's column. As advance guard to the column, Mair and his men stormed and secured Te Hārema pā near the Whirinaki River on 6 May. Joining up with Colonel J. H. H. St John's column at Ruatāhuna, the combined forces foraged and systematically destroyed settlements and food supplies of the Tūhoe tribe, which had offered sanctuary to Te Kooti. A reconnaissance party sent to investigate the failure of Colonel J. L. Herrick's column to reach Ruatāhuna skirmished with and repulsed Te Kooti's vanguard. Mair took a prominent part in this action. But sickness and an acute shortage of provisions and ammunition forced the withdrawal of government forces in mid May, before the main objective of the invasion could be achieved.
In February 1870 Mair, returning to Rotorua with an Arawa contingent, intercepted Te Arawa elders in the act of negotiating with Te Kooti. Mair immediately seized the initiative, threw down the flag of truce and attacked Te Kooti and his followers. A long running fight ensued. Te Kooti escaped to the Urewera but lost several men, including one of his most loyal and able followers, Peka Mākarini (Edward Baker McLean). In recognition of Mair's quick-wittedness, outstanding leadership and personal courage in this action he was promoted to the rank of captain on 7 February 1870 and awarded the New Zealand Cross on 1 April 1886. At the time it was believed that Mair had prevented a massacre of the inhabitants of Rotorua while their fighting force was away. However, Te Kooti's real purpose remains unclear. He may have planned to exact revenge on Te Arawa by a treacherous ruse or he may have simply intended to replenish his supplies.
Mair trained and commanded an irregular guerilla unit of 100 young Te Arawa men, the Arawa Flying Column, in the final campaigns against Te Kooti from 1870 to 1872. The unit was stationed at Kaiteriria, on the south-west tip of Lake Rotokākahi. In a series of expeditions Mair and his company scoured the Urewera in pursuit of Te Kooti and his followers. On 15 August 1871 Mair attacked a fortified camp at Waipaoa, east of Lake Waikareiti, but Te Kooti managed to escape by a hair's breadth. Subsequent forays discovered no trace of the fugitives and Te Kooti finally found sanctuary in the King Country.
In his short military career Mair displayed a degree of initiative, skill and reckless courage that singled him out from other officers. He excelled in the use of guerilla techniques of bush warfare, which allowed scope for initiative. A bold and unorthodox commander, he did not always wait for official approval before acting. He identified closely with Te Arawa who served under him and led them into battle in traditional Māori fashion, which may explain the unusual degree of influence he had over them.
Although Mair was a willing participant in the New Zealand wars, and a ruthless enemy in battle, he was aware of the complexities and moral implications of the campaigns, and sensitive to the views of his Māori opponents. After meeting Te Kooti at Matatā on 12 January 1884, Mair wrote, 'He is a wonderful man and still exercises great influence over his large following.' Years later Mair provided historian James Cowan with information and accounts of his experiences for volume two of The New Zealand wars (1923). He also recorded his recollections of the wars in Reminiscences and Māori stories (1923).
Mair held a variety of civil appointments in the post-war years, but he was restless and adventure seeking, and never achieved financial success. As government land purchase commissioner his personal influence with Ngāti Manawa assisted the Crown in the purchase of the Kāingaroa Plains. He was later critical of methods employed by the government in acquiring Māori lands. For periods he acted as interpreter to the House of Representatives, government agent at Tauranga, native resident magistrate, president of the Ikaroa Māori Land Board and member of the Arawa Māori Land Council. He also farmed at Foxton, Waihī, Rerewhakaaitu and Ōhope. In 1881 he acted as aide de camp to Lieutenant Colonel J. M. Roberts, who commanded the forces that marched against Parihaka.
On 19 September 1888 at Wellington, in his mid forties, Mair married Eleanor Catherine (Kate) Sperrey, an artist, who died five years later. They had two children: a son, John Gilbert, who died in childhood, and a daughter, Kathleen Irene (or Airini). He had earlier had two sons and a daughter with Keita Kupa from Ngāti Tūwharetoa.
For over 50 years Mair acted as official guide, interpreter and host to royalty and notable visitors to the Hot Lakes District, and in 1901 he organised the official celebrations in Rotorua for the Duke and Duchess of Cornwall and of York. He maintained his unique association with Te Arawa, enjoying close personal friendships with many of the chiefs he had fought alongside. His intuitive understanding of Māori culture and values and his command of Māori language earned him the mana of a rangatira. In 1922 Te Arawa voted Mair an annuity of £100 for his lifetime from the Arawa Lakes Fund.
Mair was a keen and not always completely ethical collector of Māori artefacts. His collection was deposited in and later purchased by the Auckland Institute and Museum. As an agent for Alexander Turnbull, Sir Walter Buller and the Auckland and Dominion museums, Mair assisted in the purchase and removal of many valuable Te Arawa carvings from the Rotorua district. These activities did not seem to diminish his standing with Te Arawa.
Mair died in Tauranga on 29 November 1923. His funeral cortège, in procession from Tauranga to Rotorua, was received and farewelled by Te Arawa on their marae at Maketū, Tāheke, Ōhau and Ōhinemutu. He is one of the few Pākehā to be buried in the cemetery of Te Arawa at Ōhinemutu.