Add Category
From September 12, every Australian who has registered to vote will received a letter asking them, "Should the law be changed to allow same-sex couples to marry?"
The result won't be known until November 15.
It's been a long process -- a national vote was first proposed by the government in 2015, when Australia was already far behind many other English-speaking nations when it comes to same-sex unions.
What do Australians think about gay marriage?
Almost every poll in the past decade has shown a majority of Australians support same-sex marriage.
The latest Newspoll survey, released on August 22, said 63% of Australians were in favor of legalizing marriage between two men or two women. Just 30% said they were opposed, with the rest undecided.
Gay rights in Australia haven't always been fast to arrive -- homosexual sex was illegal in parts of Australia up until 1997 -- but on marriage equality their opinion now seems clear.
Why is it taking so long?
In short, politics.
Since then, the campaign to bring same-sex marriage to Australia has slowly ramped up but no government has committed to passing it.
In 2013, outspoken conservative and former trainee priest Tony Abbott became prime minister, apparently eliminating all hope of same-sex marriage during his term in office.
To hold the plebiscite, the government needed money and to get that money it need to pass legislation through Australia's parliament.
Two attempts at passing legislation in 2016 and 2017 failed after the opposition Labor party and Greens party helped block it, calling for a simple parliamentary vote legalizing marriage equality instead.
After the last attempt, the government, now under Prime Minister Malcolm Turnbull, said it would instead hold a national postal vote
"This is about the world of politics, not the Australian people. The Australian people have made their minds up on marriage equality a long time ago," Tiernan Brady, executive director at the Equality Campaign, told CNN.
"Australia has a higher approval rating for marriage equality than some countries that have marriage equality," added Brady.
Why were same-sex marriage advocates opposed to the vote?
Campaigners fear that a brutal and vicious campaign against same-sex marriage by opponents could be damaging to LGBT people. They say the issue should be decided by parliament, which could in theory to legalize same-sex marriage at any time.
"This is a debate in the public sphere about (LGBT people's) worth in society, their value and that's a hard debate to be a part of," Brady said.
But prime minister Turnbull told LGBT Australians they had to trust their fellow voters.
"Australians are able and have demonstrated that they can have a respectful discussion," he said.
Adding to the drama was a court challenge made by gay marriage proponents, who said the postal vote was unnecessary and a waste of public funds.
But a unanimous vote by Australia's High Court on September 7 allowed the vote to go ahead.
Australia is not the first country to have a national vote on same-sex marriage -- Ireland voted to legalize marriage equality in 2015.
"(But Ireland) had to have a referendum because it was a constitutional requirement," Brady said. "We've always said the way this should be done (in Australia) is the way all issues pertaining to people's rights are dealt with, by parliament."
If Australians vote 'yes' is gay marriage legal?
Unlike Australian federal elections, where voting is compulsory, the postal vote is voluntary and also non-binding.
This means the government is not legally obliged to do anything and would have to pass legislation to make same-sex marriage law if Australia votes in favor.
Turnbull has said he will introduce legislation if same-sex marriage is approved by the population, but several conservative politicians have already said they'd vote against same-sex unions no matter what the postal vote says.
Defending the postal vote, the prime minister said his government was obligated to carry out a national vote as that was what he had promised voters at the last election.
"Strong leaders carry out their promises. Weak leaders break them ... You heard me, again, say again and again that every Australian will have a say on this issue," he told journalists in August.
Opposition Labor party leader Bill Shorten has repeatedly pledged to make same-sex marriage law quickly if he is elected as prime minister, but has also said he would campaign for a "yes" vote in the postal vote.