Since the first citizenship ceremony was completed in 1949, a total of 4.5 million people have become Australians, the latest figures show.
Minister for immigration and citizenship Chris Bowen explained that this is a significant milestone for Australia, as many people arriving in the country prior to 1949 had been considered British.
The first seven people to undergo the inaugural ceremony were from Spain, Greece, Czechoslovakia, France, Norway, Yugoslavia and Denmark.
During the 1970s, there was an influx of people coming from Italy, Greece and Lebanon, while more recent years have seen individuals from China, New Zealand, India, Vietnam and South Africa becoming citizens.
"Australian citizenship is unique. It carries responsibilities and grants privileges. It represents commitment to our country, to our people and to the values we all share," he commented.
Immigration lawyers may have been involved in helping a large number of these people get their documents in order so they could retain the legal right to stay in Australia.
Mr Bowen revealed that in 2010-11 alone, nearly 100,000 people were named Australian citizens - the four million mark was met back in 2007.
Citizenship ceremonies include the requirement for a pledge to be made by the individual, through which they demonstrate their public commitment to Australia and accept the responsibilities of being a resident.
There are several circumstances in which it is possible to apply for Australian citizenship - for example, you may be the spouse or partner of an existing resident, or be a New Zealander living in the country.
Other situations where an application might be made is if you are a migrant with permanent residence or are the child of a former Australian citizen.
A number of documents need to be submitted with an application, including those that supply proof of identity, good character and other supporting paperwork.
Proof of identity documents are necessary for adults and children alike and must include a current photograph and signature, evidence of a residential address and date of birth.
If a migrant with permanent residence is making an application, then they must have a valid visa that enables them to stay in Australia indefinitely.
It is important to note that being a long-term resident of the country or having the ability to vote does not automatically make you an Australian citizen - long-term residents must provide evidence of when they arrived in the country.