UNIT Australia was UNIT's branch in Australia. They had an underwater base, the Underbase, located in Sydney harbour.
Lieutenant Colonel Hardy ran the Australian branch of UNIT in 1985. (PROSE: Memories of the Future)
In the late 2000s, Colonel Tom McCay commanded UNIT Australia. In 2008, UNIT Australia saw off an advance party of Ice Warriors. The following year they began encountering temporal phenomena around Sydney bay, including manifestations of dinosaurs, and worked with the Tenth Doctor and Majenta Pryce to investigate. They were compromised from within by Fanson, who had infiltrated UNIT on the behalf of the Skith Leader who was seeking to reunite with his people who were responsible for the phenomena. The Doctor, Majenta and McCay were captured after the Leader took over nunerous UNIT personnel and brought to his people's ship. The three were able to deactivate the ship's cloaking, enabling the Underbase's guns to fire on it. (COMIC: The Age of Ice)
In the 2010s UNIT Australia enlisted the help of Harry Sullivan following the sighting of an Ice Warrior spacecraft in the desert. (AUDIO: The Enemy Beyond)