Transit visa (Subclass 771)
This visa allows people to transit through Australia for up to 72 hours while on their way to another country. A transit visa is required even if you fly out on the same plane and from the same airport which you arrive, or you stay in the transit lounge and do not leave the airport.
You will not need a transit visa if you qualify for transit without a visa.
For further information and to apply visit: Department of Home Affairs - Transit Visa (Subclass 771) page.