In 1909 the Admiralty proposed the creation of a Pacific fleet consisting of three fleet units to be operated by Imperial forces in the Pacific region. Each fleet unit would be built around a battle-cruiser. One of these fleet units would comprise the Royal Australian Navy. With Australian Government agreement to this concept, work was commenced on the battle-cruiser HMAS Australia. On completion she sailed for Australia and, on 4 October 1913, led the cruisers and destroyers of the fleet unit into Sydney Harbour to public acclaim.
With the outbreak of the First World War, Australia became the flagship of the force that captured the German colonies in the southern Pacific. She led a force which captured Rabaul on 13 September 1914 before proceeding to Samoa.
With no German forces left in the South Pacific, Australia was deployed to the United Kingdom. En route she sank the German auxiliary Eleanore Woermann. On 8 February 1915 she became flagship of the 2nd Battle-cruiser Squadron of the Royal Navy's Grand Fleet.
Australia's service with the Grand Fleet consisted of a series of frequent patrols and exercises. She was twice rammed, firstly on 22 April 1916 by HMS New Zealand. This led to her missing the Battle of Jutland which, considering the disastrous losses in the Battle-cruiser Force, may well have been fortunate. She was rammed again by HMS Repulse in December 1917. Australia carried out experimental aircraft operations in 1918 and led the port column of the Grand Fleet at the surrender of the German High Seas Fleet.
Returning home in 1919, Australia suffered a mutiny upon reaching Fremantle, Western Australia. Quite obsolete, she became a training vessel in Westernport until scuttled off Sydney Heads on 12 April 1924.