The flag of Australia is based on the British Blue Ensign—a blue field with the Union Jack in the upper hoist quarter—augmented with a large white seven-pointed star and a representation of the Southern Cross constellation, made up of five white stars. Australia also has a number of other official flags representing its people and government bodies.

The Blue Ensign is a flag, one of several British ensigns, used by certain organisations or territories associated or formerly associated with the United Kingdom. It is used either plain or defaced with a badge or other emblem.