Which mountain range runs along the eastern coast of mainland Australia?

The Great Dividing Range runs broadly parallel to the eastern coast of mainland Australia and forms the country's major highland and watershed system.

It is not one continuous wall of mountains. Instead, the name covers a vast complex of ranges, plateaus, escarpments and uplands extending for more than 3,500 kilometres from Cape York Peninsula in Queensland through New South Wales and Victoria. It eventually fades into western Victoria.

The range is called “dividing” because its crest separates drainage flowing east toward the Pacific Ocean, Tasman Sea and Bass Strait from rivers flowing inland into systems such as the Murray–Darling Basin. This makes it central to Australia's water geography.

The Australian Alps, Blue Mountains and Snowy Mountains are important ranges or regions within the larger system, not usually the best answer to this broad question. Mount Kosciuszko, Australia's highest mountain at 2,228 metres, lies in the Snowy Mountains section of the Great Dividing Range.