The flag of Australia has a blue background, with the Union Jack in the canton, a white seven-pointed star below the Union Jack, called the "Commonwealth Star", and a representation of Crux in the fly half of the flag, in white seven-pointed stars, but the star representing ε Crucis is a five-pointed star.
The Union Jack represents the United Kingdom, which Australia once was a territory of. The blue possibly represents the Pacific and Indian Oceans, although this is not certain. The seven-pointed star represents the six states of Australia, and all other territories belonging to Australia. The six stars possibly represent the six states. Crux is a symbol of the Southern Hemisphere.