Since there is no requirement on Irish citizens to register at Irish diplomatic missions or consular offices, there is no accurate means of measuring the number of Irish citizens in any particular country.
Estimates by the Australian Department of Immigration and Ethnic Affairs put the number of Irish-born people living permanently in Australia at around 100,000. However, as the number of Irish citizens would include children and grandchildren of Irish-born people, the total number of Irish citizens living in Australia would be much greater.
There is also no accurate means to measure the number of people of Irish descent living in Australia. Academic experts differ in their estimates, but a generally accepted figure would be in excess of 6 million or something approaching one third of the population.