There were loud cheers, hugs and sustained clapping in the 150-seat lower House of Representatives when all but four MPs voted in support of marriage equality, after the upper house Senate passed the bill 43-12 last week.
"What a day for love, for equality, for respect! Australia has done it," Prime Minister Malcolm Turnbull told the House.
"Every Australian had their say and they said it is fair, get on with it!"
The historic reforms will commence on Saturday, when same-sex couples can a lodge a notice to marry. They will then have to wait a month before tying the knot.
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"A time to build, a time to love, and is now at last a time for marriage equality," he said.
Same-sex marriage campaigners converged outside parliament in the nation's capital Canberra to celebrate the historic occasion, which sees Australia join more than 20 other countries in recognising such unions.
The bill was tabled in parliament by the conservative government after Australians last month endorsed the reforms in a controversial voluntary postal vote.
Nearly 80 per cent of eligible voters took part in the poll, and almost 62 per cent of the 12.7 million people who participated chose "yes" on their postal ballots.
It was opposed by proponents of same-sex marriage, who wanted direct legislative action and argued a poll would expose gay people and their families to hate speech.
Just under five million people voted "no", with conservative politicians using their rejection of gay marriage as a catalyst to push for religious exemptions to be included in the bill.
But after lengthy debate, both houses of parliament knocked back amendments to the bill, including from former prime minister and staunch "no" campaigner Tony Abbott, on religious freedom.
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