Same-sex couples will be able to marry from early January after the Governor-General signed off on new marriage equality laws on Friday.
There was celebration in the chamber as the new laws cleared parliament unchanged on Thursday after a marathon debate lasting 56 hours.
The bill was passed unanimously but the four MPs who voted against the bill were seated alone in the House of Representatives.
Queenslander Bob Katter, Hinkler MP Keith Pitt, Maranoa MP David Littleproud and McMillan MP Russell Broadbent were the only members to not vote 'Yes' to the bill.
While The House of Representatives has not confirmed how many MPs abstained, a number left during the final reading of the vote.
This was classed as failing to support the bill.
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Tony Abbott, Andrew Hastie, Barnaby Joyce, Michael Sukkar, Kevin Andrews, Scott Morrison, Alex Hawke and George Christensen all effectively abstained from supporting the bill, The Australian reported.
Governor-General Sir Peter Cosgrove gave the laws royal assent on Friday morning when he was visited by Prime Minister Malcolm Turnbull and Attorney-General George Brandis in Canberra.
"It is now part of Australian law," an elated Mr Turnbull said.
Earlier the prime minister did the rounds of morning television encouraging his fellow Australians to start making wedding preparations.
"It is a big Australian hug for all same-sex couples, saying we love and respect you, now go out there and get married," he said.
Mr Turnbull described the postal survey as a game-changer for the issue, now resolved after years of debate.
Same-sex couples will be able to lodge formal intentions to wed from Saturday allowing them to marry from January 9.
Gay couples who tied the knot overseas will have their unions officially recognised.