The flag of Australia is blue with the flag of the UK (the Union Jack) in the upper hoist-side quadrant, and a large seven-pointed star (representing the seven main states and territories in Australia) in the lower hoist-side quadrant; the remaining half is a representation of the Southern Cross constellation in white with one small five-pointed star and four, larger, seven-pointed stars.
The flag was proclaimed by the monarch in 1904 after a design competition (for which the rules implied that a British ensign flag was required). This flag was mainly intended for naval use. Throughout the first fifty years of the Australian colony, the Union Jack was widely used, as was the "Red Ensign" - the same design with a red background. It was not until 1954 that this flag became the official Australian flag, and it was not until well into the 1960's that the national flag usurped the Union Jack completely in public consciousness.
Some Australians dislike the presence of the Union Jack on the current flag, and its very close similarity to the flag of New Zealand has also posed practical problems on occasion. However, the flag retains majority support for the moment and debate on the matter is unlikely to resume seriously until after the issue of republicanism in Australia is resolved definitively one way or the other.
The Red Ensign is used by Australian merchant ships, and there is also a white Naval Ensign and a light blue Air Force Ensign.