HMAS Sirius was a commercial tanker purchased by the Royal Australian Navy and converted into a fleet replenishment vessel to replace HMAS Westralia. She was named in honour of HMS Sirius of the First Fleet. Launched in South Korea on 2004, and converted in Western Australia, Sirius was commissioned in 2006; three years before a purpose-built vessel would have been built, and at half the cost. The tanker was decommissioned in 2021 and subsequently scrapped.

HMAS Westralia was a modified Leaf-class replenishment oiler which served with the Royal Australian Navy (RAN) from 1989 to 2006. Formerly RFA Appleleaf (A79), she served in with the British Royal Fleet Auxiliary (RFA) from 1975 to 1989. The ship was initially leased to the RAN, then purchased outright in 1994. In 1998, a fire onboard resulted in the deaths of four sailors. Westralia was decommissioned in 2006, and the ship was sold into civilian service for use as a Floating Production Storage and Offloading vessel, under the name Shiraz. However, the ship was laid up in Indonesia until late 2009, when she was sold to a Turkish ship breaking company. Arriving in January 2010, the vessel was scrapped.