Same-sex couples will on Saturday begin submitting their "intended marriage" forms which include new categories of "partner" and gender "x" after the governor-general signed-off the newly passed marriage laws.
Sir Peter Cosgrove gave the laws royal assent on Friday morning, while the new forms which give a month's notice of a couple's intended marriage went online.
"It is now part of Australian law," an elated Prime Minister Malcolm Turnbull said after he and Attorney-General George Brandis visited the governor-general.
The new attorney-general's department "notice of intended marriage" form replaces the old one on Saturday, with the first same-sex weddings expected to follow a month later on January 9.
The form has a new heading Party 1 and Party 2 replacing Bridegroom and Bride, with a "Description of party" section offering three options: "groom", "bride" and "partner".
As well, there are three boxes for gender: "male", "female" and "x" - which is described as "indeterminate, intersex or unspecified".
One of those quick to make the most of the law change is Australia's ambassador to France, Brendan Berne, who posted a video on the embassy's Facebook page of his proposal to his partner of 11 years, Thomas.
"Now, as Australia has just approved marriage equality it is my turn ... to ratify my relationship," he said in French.
Mr Turnbull described the enacting of the laws as a "big Australian hug for all same-sex couples".
He criticised Labor for not progressing the matter when in office but said the victory now belongs to the whole parliament.
However, a Labor spokesman told AAP this ignored the fact that at every opportunity in the parliament, bar one, to support same-sex marriage laws Mr Turnbull had voted "no".
Labor leader Bill Shorten said many Australians found the survey experience pretty tough and now is a time for healing.
"I think we got to marriage equality in spite of Malcolm Turnbull, not because of him," he told reporters in Sydney.
Mr Turnbull rejected concerns from coalition ranks that the laws would put religious freedoms or traditional marriage at risk.
"People that think gay people making a commitment is a threat to their marriage fails to realise that the real threat is lack of commitment," Mr Turnbull said.
Attorney-General George Brandis said the "explosion" of joy in parliament on Thursday when the laws passed was "something that was unforgettable".
"Of all the things I've done since I've been in parliament I think this is the one that will be most consequential," he told ABC radio on Friday.
The new laws cleared parliament unchanged on Thursday evening after a marathon debate lasting 56 hours and despite a push from conservative MPs for additional religious protections.
Only four MPs in the House of Representatives voted against the private bill, a week after the legislation was agreed to by the Senate.
Gay couples who tied the knot overseas will now have their unions officially recognised.
A review into religious freedom will report in March, which could lead to further law changes.