Same-sex marriage could be legal as soon as Friday after a bill to change the Marriage Act passed the House of Representatives.
The Lower House chamber erupted in applause when the final vote count was announced on Thursday.
The overwhelming majority of MPs voted in favour of the bill, with only four MPs voting no.
A rainbow flag was unfurled in the chamber as MPs cheered, clapped and hugged.
Shortly after the bill was passed, the packed public gallery started singing the well-known Australian song ‘I Am Australian’.
Independent Bob Katter, and Liberals David Littleproud, Keith Pitt and Russell Broadbent were the only MPs who voted no.
“What a day for love, for equality, for respect. Australia has done it,” a beaming Prime Minister Malcolm Turnbull said.
“So, as it is written that there is a time for everything, and a season for every activity under the heavens, it is now time to heal,” Opposition Leader Bill Shorten said.
“A time to build, a time to love, a time to love, and is now at last a time for marriage equality.”
The bill has cleared both houses after passing the Senate last week and now only requires approval from the Governor General, a formality that will likely happen on Friday.
Thousands of same-sex couples living in Australia who were married overseas will instantly have their unions recognised under the law.
But same-sex weddings will not happen in Australia until January 2018 because same-sex couples will still need to lodge a Notice of Intended Marriage, which must be completed a month before the wedding.
The legal change brings Australia into line with the majority of the English-speaking world, with same-sex marriage already legal in 25 countries including Canada, New Zealand, the United States and the UK (excluding Northern Ireland).
It follows years of campaigning from the Australian LGBTIQ community and dozens of failed attempts to change the law.
The bill to legalise same-sex marriage, known as the Smith bill, passed both houses without amendments despite attempts from conservative MPs and senators to add additional religious protections.
Proposed amendments by Coalition MPs including former prime minister Tony Abbott and Treasurer Scott Morrison were voted down. Changes suggested by the Greens were also defeated.
Liberal MP Michael Sukkar’s amendment to keep two definitions of marriage – one for same-sex couples and one for heterosexual couples – was also roundly defeated, with many of Mr Sukkar’s Coalition colleagues voting against his motion.
While the Smith bill allows churches and religious celebrants to refuse to marry same-sex couples, some conservatives wanted the right of refusal extended to civil celebrants with a “conscientious objection”.
Any amendments would have delayed the passage of the bill until at least next week as the changes would have been sent back to the Senate.
Last month, the results of the government's voluntary postal survey were announced by the Australian Bureau of Statistics.
The Australian people voted in favour of change by 61.6 per cent, triggering Prime Minister Malcolm Turnbull's promise to change the Marriage Act by Christmas.
Despite some early criticisms that the use of the postal system would make the survey inaccessible, an overwhelming 79.5 per cent of Australian voters participated in what the ABS's chief statistician called an "outstanding" turnout.
