The ACT is just months away from becoming the first Australian jurisdiction to legalise same-sex marriage.
Attorney-General Simon Corbell told Fairfax Media the Labor-Greens government plans to introduce legislation into the ACT Legislative Assembly during the spring sittings.
The disclosure comes days after NSW announced it would hold a conscience vote on a private member's bill on the issue by the end of the year.
Australian states and territories have historically held back from introducing same-sex marriage over arguments that federal parliament has sole responsibility for marriage equality and state-based laws would be constitutionally invalid.
But a report, published on Friday, found it was lawful for NSW to legislate on same-sex marriage.
The finding supports an ACT- commissioned opinion by now High Court judge Justice Stephen Gageler from 2009, which confirmed a same-sex marriage law could be constructed that did not conflict with the Commonwealth Marriage Act.
Mr Corbell said the ACT government was confident it had the constitutional authority to legislate and were on track to introduce a bill some time in spring.
The ACT has been a leader in same-sex marriage laws, with the assembly reinstating the role of ceremonies and celebrants in civil unions in last August, giving same-sex couples the same rights as people married under the Marriage Act.
The legislation restored the ACT government's original civil union laws, which were overturned in 2006 by the then Liberal federal government, which said they were too similar to marriage.
"The ACT first started agitating for reform in this area way back in 2006," Mr Corbell said.
"We were leading the country at that time as one of the first jurisdictions to legislate in this space for what was then a civil union scheme.
"Since then there's been massive steps. We've seen the debate move from civil unions to same-sex marriage within three to five years and at the same time we've seen massive shifts within the left-of-centre political parties, particularly my own party, on the importance on reform."
Mr Corbell said he was confident the imminent reforms would pass through the Assembly.
He said there had been a strong level of community support for the cause, which some sections of the political process and some governments had been slow to recognise.
"But there is now a real head of steam building on this issue within Australia; it's inevitable that we will have a same-sex marriage scheme, either at a territory, state or national level very soon.
"I'm confident the ACT could be one of the first, if not the first, jurisdiction to have such a thing, but I still think it's highly likely it will be the ACT that legislates first in the space because of the clear majority on the floor of Assembly in a single-chamber parliament."