Since I am currently living in Australia, I will dedicate this post to the Australian flag.
The Australian flag is blue and has the flag of the United Kingdom in the upper left corner and a large seven-pointed star, know as the Commonwealth or Federation Star, below it. The star represents the federation of the colonies of Australia in 1901. On the other hand, the stars on the other side in white with one small five-pointed star and four larger, seven pointed stars is a representation of the Southern Cross constellation.
Besides that, Ashmore and Cartier Islands, islands in the Indian Ocean, midway between northwestern Australia and Timor island, uses the same flag as well. The reason for this is that the uninhabited islands came under the Australian authority in 1931.