1900 in Australia
Governors of the Australian colonies
- Governor of New South Wales — William Lygon, 7th Earl Beauchamp
- Governor of Queensland — Charles Cochrane-Baillie, 2nd Baron Lamington
- Governor of South Australia — Hallam Tennyson, 2nd Baron Tennyson
- Governor of Tasmania — Jenico Preston, 14th Viscount Gormanston (until 14 August)
- Governor of Victoria — Thomas Brassey, 1st Earl Brassey (until 31 March)
- Premier of New South Wales — William Lyne
- Premier of South Australia — Frederick Holder
- Premier of Queensland — Robert Philp
- Premier of Tasmania — Elliott Lewis
- Premier of Western Australia — John Forrest
- Premier of Victoria — Allan McLean (until 19 November), then George Turner
- 3 January — Electric lighting is installed on Adelaide streets.
- 25 January — State Labour politicians meet in Sydney to formally found the federal Labour party.
- 25 March — The S.S. Glenelg is wrecked off the Victorian coast, resulting in 31 deaths.
- March to May - Record rainfall and flooding affect the Pilbara and Gascoyne regions of Western Australia
- 9 May — The Sierra Nevada is wrecked off Portsea, Victoria; 23 lives are lost.
- 2 July - Snow falls to extremely low levels in New South Wales, being recorded as low as Forbes.
- 5 July — The Commonwealth of Australia Constitution Act (UK) is passed.
- 24 July — Neville Howse rescues a fallen ally under heavy fire during the Second Boer War, becoming the first Australian recipient of the Victoria Cross.
- 8 August — The first Australian contingents of naval volunteers set sail for China to assist British and international troops during the Boxer Rebellion.
- 17 October — Natural gas is found at Roma in Queensland
- 27 October — Notorious murderer Jimmy Governor is apprehended near Wingham, New South Wales.
- 15 December — Upon his arrival in Australia, the first Governor-General, Lord Hopetoun, commits the so-called Hopetoun Blunder.
- 13 September — The film Soldiers of the Cross is shown in Melbourne, one of the first films shown in Australia. (IMDb entry)
- 25 January — Harold Raggatt, public servant (died 1968)
- 29 March — John McEwen, caretaker Prime Minister (1967–1968) (died 1980)
- 19 October — Bill Ponsford, cricketer (died 1991)
- 20 October — Jack Lindsay, writer (died 1990)
- 3 December — Albert Hawke, Premier of Western Australia (1953–1959) (died 1989)
- 17 July — Thomas McIlwraith, former Queensland premier (born 1835)
- 17 November — John Ferris, Australian cricketer (born 1867)
- About 4000000