The Ash Wednesday bushfires hit South Australia and Victoria on 16 February 1983. The total death toll was 75 (47 in Victoria, 28 in South Australia), around 2,500 homes were destroyed, hundreds of thousands of livestock lost, and an estimated half a million hectares were burnt out. Both states declared a state of disaster.

A period of drought in 1982 in the eastern areas of Australia had left tinder dry vegetation that was quickly incinerated by the fires, some of which had been started by arsonists. A cold front over the Great Australian Bight caused hot air from central Australia to be drawn southwards creating a hot northerly wind over the south-eastern states. Temperatures of over 40 °C (the peak recorded temperature in South Australia was 43 °C), low humidity and these gusty conditions meant that the fires were difficult to get under control.

The worst affected areas were the Mount Lofty Ranges in South Australia and the Macedon area and Dandenong Ranges of Victoria. Around Mount Gambier, fire burnt grassland at an average speed of 17 kilometres an hour. This fire, known as the Clay Wells fire, was the biggest single fire and burnt more than 120,000 hectares. The total cost of loss or damage to private property in South Australia was estimated at over $200 million.