The Murray River, or River Murray and sometimes informally referred to as the "Mighty Murray", is Australia's second-longest river in its own right (the longest being its tributary the Darling). At 2,575 kilometres (1,600 miles) in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it flows to the northwest, before turning south for its final 500 kilometres or so into South Australia then ends at the mouth at Lake Alexandrina.

The waters of the Murray flow through several lakes that fluctuate in salinity (and were often fresh until recent decades) including Lake Alexandrina and The Coorong before emptying through the Murray Mouth into the southeastern portion of the Indian Ocean, often referenced on Australian maps as the Southern Ocean, near Goolwa. Despite discharging considerable volumes of water at times, particularly before the advent of large scale river regulation, the Mouth has always been comparatively small and shallow.