Mabo was born Eddie Koiki Sambo but he changed his surname to Mabo when he was adopted by his uncle, Benny Mabo. He was born on the island of Mer (Murray Island) in the Torres Strait between mainland Australia and Papua New Guinea.
Mabo married Bonita Neehow, an Australian South Sea Islander, in 1959. The couple had seven children and adopted three more. One daughter, Gail, is an Aboriginal artist and dancer who works with schools in New South Wales as a cultural advisor and serves as the family's designated spokesperson.
Mabo worked on pearling boats, as a cane cutter, and as a railway fettler before becoming a gardener at James Cook University in Townsville, Queensland at the age of 31. The time he spent on the campus had a massive impact on his life. In 1974, he was talking with JCU historians Noel Loos and Henry Reynolds, and Loos recalls:
we were having lunch one day in Reynolds' office when Koiki was just speaking about his land back on Mer, or Murray Island. Henry and I realised that in his mind he thought he owned that land, so we sort of glanced at each other, and then had the difficult responsibility of telling him that he didn't own that land, and that it was Crown land. Koiki was surprised, shocked and even ... he said and I remember him saying 'No way, it's not theirs, it's ours.'
Later, when Mabo was a research assistant on an oral history project in the Torres Strait, Reynolds records:
He got as far as Thursday Island and no further. He was refused permission to land on any of the other islands in the Straits[sic]. A reputation as a radical was a heavy burden in Queensland at the time. For Eddie the rejection was devastating. He could not go home. He was not only landless in the eyes of white man's law, he was an exile as well.
In 1981 a land rights conference was held at James Cook University and Mabo made a speech to the audience where he explained the land inheritance system on Murray Island. The significance of this in terms of Australian common law doctrine was taken note of by one of the attendees, a lawyer, who suggested there should be a test case to claim land rights through the court system. Perth-based solicitor Greg McIntyre was at the conference and agreed to take the case; he then recruited barristers Ron Castan and Bryan Keon-Cohen. McIntyre represented Mabo during the hearings.
Of the eventual outcome of that decision a decade later, Henry Reynolds said: "it was a ten year battle and it was a remarkable saga really."
On 21 January 1992, he died of cancer at the age of 55.
Five months later, on 3 June 1992, the High Court announced its historic decision, namely overturning the legal doctrine of terra nullius – which is a term applied to the attitude of the British towards land ownership on the continent of Australia.
That decision, formally "Mabo v Queensland (No 2)", now commonly called "Mabo" in Australia, is recognised for its landmark status. Three years after Mabo died, that being the traditional mourning period for the people of Murray Island, a gathering was held in Townsville for a memorial service.
Overnight, Mabo's gravesite was attacked by vandals who spray-painted swastikas and the word "Abo" (a derogatory slang term for an Aboriginal person) on his tombstone and removed a bronze bas-relief portrait of him. His family decided to have his body reburied on Murray Island. On the night of his re-interment, the Islanders performed their traditional ceremony for the burial of a king, a ritual not seen on the island for 80 years.
In 1992, Mabo was posthumously awarded The Australian Human Rights Medal in the Human Rights and Equal Opportunity Commission Awards, together with the Reverend Dave Passi, Sam Passi (deceased), James Rice (deceased), Celuia Mapo Salee (deceased) and Barbara Hocking. The award was in recognition "of their long and determined battle to gain justice for their people" and the "work over many years to gain legal recognition for indigenous people's rights".
In 1993 The Australian commemorated his work by voting him the 1992 Australian of the Year (not to be confused with the official Australian of the Year awards issued by the Australian Government).
A documentary, Mabo: Life of an Island Man, directed by Trevor Graham was released in 1997 (and received the AFI Award for Best Documentary).
On 21 May 2008, James Cook University named its Townsville campus library the Eddie Koiki Mabo Library.
Mabo Day is an official holiday in the Torres Shire, celebrated on 3 June.
On 10 June 2012, Mabo, a television drama based on the life of Mabo was broadcast on the Australian Broadcasting Corporation (ABC).
On 24 August 2015, Tony Abbott became the first Prime Minister to visit Eddie Mabo's grave on Murray Island where he paid tribute to his legacy.
In 2016, Google Doodle commemorated his 80th birthday.