1820 in Australia
The following lists events that happened during 1820 in Australia.
- 3 May - John Joseph Therry and Philip Conolly, the first Catholic priests officially appointed to Australia, arrive at Port Jackson from Ireland.
- 19 August - Joseph Wild discovers Lake George and names the Snowy Mountains.
- 28 October - Governor Macquarie names Lake George after King George III.
- 1 December - Campbelltown, New South Wales is established.
- Sydney has 1,084 buildings – mostly single-storey dwellings – and 12,079 people.
- Sheep population in Australia - 120,000.
- Munday, Rosemary, ed. (1991). "How Australia Began: Significant Dates in Australian History". The Bulletin Australian Almanac & Book of Facts 1992. Sydney: Australian Consolidated Press. p. 2. ISSN 1038-054X.
- Cameron, Angus, ed. (1986). "Part One: Capital City Chronologies. A History of Sydney". The Second Australian Almanac: An 800-page Databank Crammed with Essential Information for Every Australian. North Ryde, NSW: Angus & Robertson. p. 4. ISBN 0-207-15232-2.
- "Sir James Martin, 1820–1886". Heritage Archives and Library Research and Collection Services. 10 December 2017.