For nearly a century, many answers to that question have been influenced by a figure developed by anthropologist Alfred Radcliffe-Brown000.
Based on the revised population figure and comparisons with early Census records, researchers estimate the Indigenous population declined by more than two million people between 1788 and 1861.
Corey Bradshaw, a professor of global ecology at Flinders University who co-led the research, told SBS News the findings illustrate the magnitude of the demographic collapse experienced by Indigenous Australians.
Researchers believe the decline was likely driven by a combination of introduced diseases, frontier violence, malnutrition, dispossession and other impacts of colonisation.
Bradshaw said the approach is less vulnerable to the biases and gaps in historical records, and each of the three methods produced a relatively congruent set of estimates.
The 1930 estimate of about 250,000, Bradshaw said, was developed at a time when researchers lacked access to modern tools.
Other historical estimates suggested the population of Indigenous Australians may have been up to one million people, still under half of what the new research suggests.
Bradshaw said understanding the size of Indigenous populations before colonisation was essential to truth-telling and reconciliation.
The Indigenous population in Australia has grown since the 1950s, and represented 3.2 per cent of the overall population at the time of the 2021 Census at just under 813,000 people.
More than 100 First Nations languages are still spoken across Australia, though some are in serious danger of being lost.