The theory has resurfaced online after lying dormant since around 2006 when the Flat Earth Society originally floated the idea.
Some 50,000 people joined the bandwagon earlier this month when Facebook user Shelley Floryd shared a status update, explaining why she thinks Australia does not exist.
She wrote: “Australia does not exist. All things you call ‘proof’ are actually well fabricated lies and documents made by the leading governments of the world.
“Your Australian friends? They’re all actors and computer generated personas, part of the plot to trick the world.”
The post has since been removed, but not before it gathered traction online.
Ms Floryd herself later revealed the post was shared online as a joke but conspiracists have found renewed interest in the supposed Australia hoax.
Many have now looked through online archives to uncover what appears to be the original claim suggesting Australia does not exist.
In 2006 a post on the the Flat Earth Society forum said: “Most of you have probably been brought up believing in the imaginary land called Australia. I bet many of you even learned about it in school. I am here to tell you the truth.
Flat Earth bombshell: Conspiracists have claimed Australia is a made up country
“Well, the fact is that Australia doesn’t really exist. Everything you have ever heard about it was made up, and any pictures of it you have seen were faked by the government.
“I am sure you have even talked to people on the internet who claim to be from Australia. They are really secret government agents who are surfing the internet to enforce these false beliefs.
“We are not entirely sure why the government made up an imaginary continent, or why it is trying to convince the world that this continent is real, but we can tell you that we know for a fact that Australia doesn’t really exist.
“Please join us in our quest to convince the world of the truth.”
The post in question was an immediate online success, gathering hundreds of affirmative replies.
Who could ever believe Australia exists?
One forum user, The Dragon Reborn, said: “Who could ever believe Australia exists? Anyone who cares to look would realise it’s all propaganda.
“Thankfully, Masterchief was quick enough to notice it. I can only pray there are others that have realised this truth.”
Flatbiker0 said: “I thought that would have been obvious. The fact that the government puts so much effort into covering it up is just more proof that the Australia Conspiracy is much bigger than the Flat Earth Conspiracy.”
The Australia hoax conspiracy was spread around on online forums
Others meanwhile rejected the theory but claimed we have been deceived about Australia in another way.
Rogherio wrote: “Australia does exist just not where you were taught it was by Round Earth science.”
However the idea that a whole country or one specific region does not exist, or the creation of made up places, is not a novel idea and is in fact one of the oldest practical joke played on the internet.
The most common example of this is the North-Rhine-Westphalia town of Bielefeld in Germany which has been labelled a government hoax since at least 1993.
Flat Earth theory claims the planet is not a globe but a flat disc instead
Back in the early days of the internet, a group of students joked online the town does not actually exist, and the rumour spread like wildfire becoming something of an inside joke among Germans.
Another example is the non-existent South American country of San Escobar which was created in an incredible blunder by Polish Minister of Foreign Affairs Witold Waszczykowski.
On 10 January 2017 Mr Waszczykowski told reporters he had established diplomatic relations “with countries such as Belize or San Escobar” – he meant San Cristóbal y Nieves, which is Spanish for Saint Kitts and Nevis.
San Escobar has since become a popular online meme and a means of mocking government blunders.