Australia has officially become the 26th country to legalise same-sex marriage after the law was passed on Thursday with the overwhelming backing of the Federal Parliament.
Thirteen years after changing the Marriage Act to explicitly forbid same-sex unions, federal politicians voted to undo the last major piece of discrimination against gay and lesbian Australians.
During the same-sex marriage debate, Liberal MP Tim Wilson proposes to his long term partner Ryan Bolger.
It followed last month's emphatic resolution of the Australian public in the postal survey to join the rest of the English-speaking world by embracing marriage equality.
The vote in the House of Representatives, minutes before 6pm on Thursday, came after last week's vote in the Senate, meaning the law has now passed both houses of Parliament.
"Australia has done it. What a day for love, for equality, for respect," declared a jubilant Prime Minister Malcolm Turnbull, who punched the air as he called it a historic day for the nation.
"This belongs to us all. This is Australia – fair , diverse, loving and filled with respect for every one of us. This has been a great, unifying day in our history."
Later, Mr Turnbull put the momentous social reform in the same category as the 1967 referendum to count Indigenous people in the census, and said he was proud it occurred under his leadership.
Fairfax Media understands a special meeting of the Executive Council has been called for Friday morning for the Governor-General to officially sign the bill into law.
Attorney-General George Brandis advised the law would formally change on Saturday, allowing same-sex couples to lodge a Notice of Intended Marriage from this weekend.
The minimum notice period is one month, meaning the first legally recognised same-sex wedding could take place on January 9.
Only four MPs voted against the change, and so clear was the result that a formal count was not required. A handful of MPs - including former prime minister Tony Abbott and Treasurer Scott Morrison - chose to abstain.
When the vote was declared on the floor of the House, the packed public gallery exploded into cheers and applause, while MPs crossed the chamber to embrace each other, waive rainbow flags and in some cases cry.
The public galleries sustained rapturous applause for several minutes and eventually burst into a rendition of I Am, You Are, We Are Australian. Some also chanted "Warren!" referring to Liberal MP Warren Entsch, a long-time gay rights advocate and ally.
Numerous well-known gay and lesbian Australians were present to witness the historic moment, including Olympic swimmer Ian Thorpe and actress Magda Szubanski.
"What an extraordinary moment," Szubanski said. "When I watched all of those people move to the 'yes' side of the House, I thought Canberra was going to tip over."
Thorpe, who struggled with his sexuality for many years and came out publicly in 2014, said it was a "momentous day" for young gay and lesbian people.
"We have created an Australia that is more equitable, more fair and more just, and it is the kind of place that more Australians want to see," he said.
Opposition Leader Bill Shorten said he was "humbled" by the momentous event and "privileged" to be part of it.
"This isn't about me or the other 150 members of Parliament - it is about Australians and Australia, the LGBTIQ people and their families and their partners," he said immediately after the vote. "We are telling them: we love you, you're equal."
While gay rights campaigners have fought for marriage equality for decades, the direct path to Thursday's vote began two years ago when the former Abbott government announced it would settle the question of same-sex marriage by a public plebiscite.
Mr Turnbull continued that policy, but it was blocked by opponents in the Senate. The government later opted to hold a voluntary postal survey asking: "Should the law be changed to allow same-sex couples to marry?"
Australians voted "yes" to that question by 61.6 per cent to 38.4 per cent, prompting the government to allow a free vote in Parliament, which passed on Thursday.
The four MPs to vote against the change were Queensland independent Bob Katter, and Coalition MPs Keith Pitt, David Littleproud and Russell Broadbent. While the votes were not formally tallied, it was clear in the chamber that close to 130 MPs voted "yes".
It followed a long day of debate over proposed amendments to Liberal senator Dean Smith's same-sex marriage bill, most of them put forward by conservative Coalition MPs opposed to change. All amendments were comfortable defeated by Labor, the crossbench and several Liberals including frontbenchers Christopher Pyne and Kelly O'Dwyer.
There were emotional scenes in Parliament House following the vote, as Labor senator Louise Pratt hugged her partner Bek and flagged their intention to marry. "It means the world to us," she said. "We've been working to this day for a really, really long time."
Veteran gay rights campaigner Rodney Croome dedicated the victory to those who had campaigned over many years, including those who had died before the law was changed. Their lobbying and activism had "built a mountain from which our legislators were able to see the truth," he said.
Alex Greenwich, the NSW parliamentarian who co-chaired the Equality Campaign, said: "We came, we saw, and love finally conquered. Marriage equality is finally the law of the land and we are so proud of Australia."