1803 in Australia
- Monarch - George III
- 14 January – Lieut-Col David Collins commissioned in England to found a new settlement on Bass Strait, preferably at Port Phillip.
- 5 March – George Howe publishes the first issue of the weekly The Sydney Gazette and The New South Wales Advertiser, Australia's first newspaper.
- 27 December – Convict William Buckley escapes from Sullivan Bay, Victoria. He lives with the Wautharong Aboriginal people for 32 years.
- 26 June – John Macarthur writes the Statement of Improvement and Progression of Fine Woolled Sheep in New South Wales.
Exploration and settlement
- January–February – Acting Lieutenant Charles Robbins and NSW Surveyor General Charles Grimes survey Port Phillip in HMS Cumberland
- 2 February – Charles Grimes discovered the Yarra River.
- 9 June – Investigator arrives in Port Jackson after circumnavigating Australia. On the voyage Matthew Flinders charted the coast and Robert Brown made an extensive collection of the flora of Australia.
- 11 September – John Bowen with a party of forty-eight found the first settlement in Van Diemen's Land near the Derwent River.
- 9 October – David Collins, on HMS Calcutta and Ocean, establishes the short-lived settlement at Sullivan Bay on Port Phillip
- 1 January – Daniel Egan, politician (died 1870)