The discovery indicates their arrival on the continent was up to 18,000 years earlier than previously thought.
It was made after sophisticated artefacts were excavated from a rock shelter in the Northern Territory.
Researchers unearthed what they say are the world's oldest stone axes and ochre crayons, thought to be used for art.
Although there is some debate, scientists have previously estimated that humans arrived in Australia between 47,000 and 60,000 years ago.
