George Nēpia was born at Wairoa, Hawke's Bay, of Ngāti Rākaipaaka of Nūhaka and Māhia. His birth date was registered as 25 April 1905, but he later claimed he was born in 1908. His father, Peta Piripoi Nēpia, and mother, Riripeti (Peti) Pirihi, separated early and each remarried. After an unhappy period with his father and stepmother, George went to live with his maternal grandmother. Living near the Taihoa marae he attended Wairoa primary school and enjoyed a happier childhood.
George Nēpia fondly recalled playing with a rugby ball, then in the evening eating 'a plentiful plate full of kai' which might include whitebait, duck eggs or Māori bread. Realising the demands on his ageing grandmother, he went back to live with his father and attended the Nūhaka Native School. Life at school was oriented to games and in the absence of a rugby ball Nēpia's school cap was subjected to rough handling and kicking.
After leaving primary school Nēpia worked on a sheep station and a railway construction gang, saving money to help pay for boarding school. The decision was made to send him to Te Aute College in Hawke's Bay. He headed off to school but, after urging from Eru Tengaio and others, spontaneously left the train with his friends who were enrolling at the Māori Agricultural College south of Hastings. His father did not forgive him for this, particularly as the Te Aute school fees had been paid.
Nēpia enrolled at the college, although he was not a member of the Mormon Church, who administered it. His mentor was the American Erwin Moser, who assisted with his fees and honed his rugby skills. He was taught to kick with skill and precision and instructed in the spiral kick, and the formative seeds of his tackling skills were implanted. Nēpia was a spectator at the South Africa – New Zealand Māoris match in Napier in September 1921, where he was impressed by the great fullback Gerhard Morkel. That year he was selected for East Coast Districts, and in 1922 was in the legendary Hawke's Bay team, initially on the wing but later at second five-eighth.
In 1924 the Te Mori Rose Bowl match between northern and southern Māori was regarded as a trial for the 1924–25 All Black team to tour the British Isles. Nēpia was moved to fullback to allow the selector's nephew to contest a tour place at five-eighth. Surprised, but eager to put every effort into his new position, Nēpia sought advice from his cousin Walter McGregor, a winger in the northern Māori team, who advised him to catch the ball on the full, tackle soundly, and put the ball out securely when kicking for touch. Two more trials saw Nēpia selected for the tour. Jimmy Mill and Lui Paewai were noted Māori team-mates.
Despite personal doubts about his own ability, which arose on the boat to England, the young Nēpia played virtually faultless rugby at fullback in all 32 games in the British Isles, France and Canada. The team won all its games, and became known as The Invincibles. Nēpia scored 77 points on tour, and was selected as one of the five players of the year by John Wisden's Rugby Football Almanack. He was noted for his fierce tackling, catching of the ball, kicking and ability to stop opposition forward rushes. On their return, Nēpia and Paewai received enthusiastic welcomes in Hawke's Bay and the East Coast.
In 1925 Nēpia played in a match to mark the opening of the church at Tikitiki. At a celebratory dance, he met Huinga Raupani Kōhere, of Ngāti Porou, who was playing the piano. Huinga's father, Lieutenant Hēnare Kōhere, had served with the New Zealand Pioneer Battalion in France in the First World War, where he died of wounds; her mother, Ngārangi, had died when Huinga was five years old. Huinga found in Nēpia far more than a highly compatible dance partner, but the couple had to endure over a year of waiting before they married, as Huinga's family undertook a range of matchmaking 'while Huinga pined and pined'. The intervention of Apirana Ngata and his wife is said to have facilitated the marriage, which by George’s account took place at Tikitiki, on 6 May 1926. Theirs was the first wedding in Tikitiki's newly carved Māori church.
George and Huinga moved to a farm at Rangitukia, with land given by her family. The footballer milked the dairy herd given by his father and worked industriously at clearing gorse. Their only daughter, Kiwi Rauponga, was named after the national rugby symbol of the fern leaf. There were also three sons.
Controversy arose over Nēpia's omission from the 1926–27 Māori team that toured France, England, Wales, Australia, Ceylon (Sri Lanka) and British Columbia. The New Zealand Rugby Football Union claimed he was not available; Nēpia apparently claimed otherwise. Omitted from the 1928 tour of South Africa because of his race, Nēpia toured Australia in 1929 where, because of injury, he played only half the first test. There he was described as 'a perfect gentleman, who sang beautifully’; he was well known for his rendition of the song 'Beneath the Māori moon'. A year later he played fullback for New Zealand in each of the four tests against the touring British Isles team. In all, Nēpia played 46 matches for the All Blacks, scoring a total of 99 points.
In 1935 Nēpia captained the New Zealand Māori team to Australia. The financial strains of the depression were reflected in his decision to play rugby league in England that year for Streatham and Mitcham, for £500. He later moved to play for Halifax. His farewells to his children, who stayed at home with Huinga, particularly affected him, and he later regretted his decision to go. In 1937 he returned to New Zealand and played league for Manukau. He was selected to play in the New Zealand team against Australia in a memorable game which saw the Kiwis win 16–15, after being down 6–15 at half time.
In 1947 an amnesty allowed league players to be readmitted to rugby union, and Nēpia played two games for East Coast. In 1950 he led the Olympians Club in a first-class game against Poverty Bay, which was captained by his son George – the only occasion when father and son have played against each other in New Zealand first-class rugby. In this match Nēpia also became the oldest New Zealander to play a first-class game.
Nēpia then took up refereeing and moved to the Wairoa district as a farm manager. His later years included employment in a Masterton factory. The death in 1975 of Huinga, who 'instructed the children to look after Papa', was a singular blow. Nēpia moved to Ruatōria sometime after 1981 and lived with his son Winston.
In 1982 Nēpia went with the New Zealand Māori team to Wales, where his reception at the St Helens ground in Swansea was an indelible mark of homage to this nonpareil of fullbacks. In 1986 he was elected by the South African Rugby Board as life vice president, and in the same year was the subject of television's This is your life.
George Nēpia died at Ruatōria on 27 August 1986. His eldest son, George, had been killed in Malaya in 1954 on active service. Kiwi, Te Ōmanga and Winston survived him.