Thousands gathered across the country to watch the Australian Bureau of Statistics announce the same-sex marriage survey result.
Marriage equality campaigners have expressed their joy and relief at the Yes result in Australia's Marriage Law Postal Survey.
Supporters of marriage equality danced to 'Love is in the Air' at an event in Prince Alfred Park, in Sydney's CBD, when the results of the postal survey were announced on Wednesday.
"Please look at the person next to you and realise you will remember this forever," Anna Brown, from the Marriage Equality campaign, told the thousands gathered.
"This is a profound moment, a moment of acceptance of celebration and - let's face it - massive, massive relief. We have won this."
Speaking at the event, Qantas CEO Alan Joyce, who has spoken out for marriage equality throughout the campaign, reflected on how his nation of birth, Ireland, had already legalised same-sex marriage in 2015.
"Today I am even more proud of Australia, the country of my selection," Mr Joyce said.
"We now send a message from the Australian people to get on with it, we now expect it, we needed to be delivered and we needed to be delivered fast. Get on and do it, Mr Turnbull."
Former Australian swimmer Ian Thorpe, who has been a prominent face of the equality campaign, said at a press conference at the event he was proud of his involvement and advocacy.
"I have been pleased I have been able to be part of it," Thorpe said.
"I feel is right not only for the LGBTI community but for the Australian community as well."
Among the crowd in Sydney was gay couple Marcel de Vere and Rob Novotny.
"It's humbling that the Australian public have come behind us in this fight," Mr de Vere told SBS News.
"It's been a long, long battle for all of us. We haven't finished yet."
The pair has no plans to marry just yet, but Mr de Vere is pushing his partner in that direction.
"He needs to propose," Mr de Vere joked.
Jess Weiss is already engaged to her partner but believes the survey result is a marked change in how the LBGTI community will be treated in the community.
"It always makes a difference to know you've got your friends and family support, but to know the country that you live in, which is meant to be an accepting country, actually is accepting and everyone really wants it, it’s nice to know that we’re back to the country we love," Ms Weiss said.
As Australian Statistician David Kalisch revealed the Yes vote had prevailed, crowds in Melbourne burst into cheers erupted with screams of joy as champagne corks exploded into the sky.
Many started dancing to Kylie Minogue's "Celebration" while clouds of rainbow dust erupted over the crowd.
"This is the happiest day of my life. I've never felt this happy," 35-year-old James Mead said as tears streamed down his face.
In Perth, Jonathon Mann was accompanied by his friend, Ally White, to hear the announcement.
"For me, it's so good to know that one of my great mates Jon can have the same rights as me and get married one day," Ms White told SBS before the pair hugged.
"They've seen what Australia has said, not just in one state or two states but all across the country," Ryan Stuart, who also attended the event in the Western Australian capital, said.
Meanwhile rain did not stop yes supporters from celebrating at Hindmarsh Square in Adelaide.
"It's an extraordinary relief for those of us who have been supporting marriage equality for an extended period of time," South Australia Premier Jay Weatherill said in a press conference.
"Very pleased South Australia registered a very strong result, above the national average.
"I think it demonstrates this sense of justice that people in South Australia have, a natural demand for equality."
- With AAP