The 1940 Australian Championships was a tennis tournament that took place on outdoor Grass courts at the White City Tennis Club, Sydney, Australia from 19 January to 29 January. It was the 33rd edition of the Australian Championships (now known as the Australian Open), the 9th held in Sydney, and the first Grand Slam tournament of the year. The singles titles were won by Australians Adrian Quist and Nancye Wynne.
See main article: 1940 Australian Championships – Men's singles. 
Adrian Quist defeated Jack Crawford 6–3, 6–1, 6–2
See main article: 1940 Australian Championships – Women's singles. Nancye Wynne defeated Thelma Coyne 5–7, 6–4, 6–0
See main article: 1940 Australian Championships – Men's doubles. John Bromwich / Adrian Quist defeated Jack Crawford / Vivian McGrath 6–3, 7–5, 6–1
See main article: 1940 Australian Championships – Women's doubles. Thelma Coyne / Nancye Wynne defeated Joan Hartigan / Edie Niemeyer 7–5, 6–2
See main article: 1940 Australian Championships – Mixed doubles. Nancye Wynne / Colin Long defeated Nell Hall Hopman / Harry Hopman 7–5, 2–6, 6–4