What is Australia's largest lake when full?

Australia’s largest lake when full is Kati Thanda-Lake Eyre. It is a vast, shallow salt lake in South Australia’s arid interior and is usually dry or covered only by a thin layer of water.

The lake’s full basin covers roughly 9,500 square kilometres, though complete filling is rare and depends on exceptional rainfall across inland Queensland and South Australia. Water travels through the inland river system, including the Diamantina and Georgina rivers, before reaching the lake.

Kati Thanda-Lake Eyre lies about 15 metres below sea level, making it Australia’s lowest natural point. In 2012, the traditional Aboriginal name Kati Thanda was formally added to Lake Eyre, honoring the Arabana people’s connection with the region.

A common mix-up is Lake Argyle, which can have a large surface area but is an artificial reservoir. Lake Gairdner and Lake Torrens are also major salt lakes, but neither exceeds Lake Eyre’s maximum area.