HMAS Pioneer was originally built for the Royal Navy and from 1905 served on the Australia Station. On 1 March 1913 she was commissioned into the RAN.
The outbreak of war saw her as a guard ship at Melbourne. She was soon ordered to Fremantle and sailed for the west coast on 6 August 1914. While patrolling off Fremantle, the Pioneer subsequently captured the German merchant vessels Neumunster and Thuringen, which were unaware of the outbreak of war.
Although intended to be part of the escort of the first AIF convoy, which left Albany on 1 November 1914, Pioneer had to withdraw due to engine problems. On 9 January 1915 she departed Fremantle for German East Africa to take part in operations against the German cruiser SMS Koenigsberg, which had sought refuge up the Rufigi River The role of the British fleet gathered off East Africa was to prevent the Koenigsberg from breaking out of the river, and to prevent supplies being brought in by sea for either her, or the German forces ashore.
Koenigsberg was destroyed by British monitors on 12 July 1915 but Pioneer remained on station, continuing her blockade duties and bombarding targets ashore. Pioneer eventually returned to Australia in October 1916 and was paid off. She was sold in 1924 and scuttled off Sydney Harbour in 1931.
Pioneer, obsolete and decrepit, saw more actual combat than any other Australian ship in the First World War.