The flag of Australia is a defaced Blue Ensign: a blue field with the Union Jack in the canton (upper hoist quarter), and a large white seven-pointed star known as the Commonwealth Star in the lower hoist quarter. The fly contains a representation of the Southern Cross constellation, made up of five white stars, one small five-pointed star and four, larger, seven-pointed stars. There are other official flags representing Australia, its people and core functions of government.

The flag's original design (with a six-pointed Commonwealth Star) was chosen in 1901 from entries in a competition held following Federation, and was first flown in Melbourne on 3 September 1901, the date proclaimed as Australian National Flag Day. A slightly different design was approved by King Edward VII in 1903. The seven-pointed commonwealth star version was introduced by a proclamation dated 23 February 1908. The dimensions were formally gazetted in 1934, and in 1954 the flag became recognised by, and legally defined in, the Flags Act 1953, as the "Australian National Flag".

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