Results released Wednesday by the Australian Bureau of Statistics revealed 61% of the population voted to allow same-sex marriage, with 38% voting against.
Rainbow-colored smoke, confetti and cheers erupted in the center of Melbourne following the announcement, where hundreds of people had gathered to hear the result.
When couple Jane Mahoney, 28, and Josie Lennie, 26, heard the result they collapsed into each others' arms in tears. "(Now) we need to save and also gets lots of fun ideas from the other gay weddings," they told CNN.
More than 12.7 million people across the country, or 79.5% of the population, took part in the survey with every state and territory returning a majority "yes."
Celebrations, singing and tears greeted the announcement in Melbourne.
It's the beginning of the end of a long-running campaign to allow marriage equality in Australia, something already legal in the majority of English-speaking countries worldwide.
Speaking after the result, Australia Prime Minister Malcolm Turnbull said it had been an "overwhelming" response in favor of "yes" and called for same-sex marriage to be legalized before Christmas.
"They voted 'yes' for fairness, they voted 'yes' for commitment, they voted 'yes' for love. And now it is up to us here in the Parliament of Australia to get on with it," he told reporters in Canberra.
Opposition Labor Party leader Bill Shorten told the Melbourne rally the postal vote itself should never have happened.
"I feel for young people who had their relationships questioned in a way I wouldn't have thought we would see ever again, but nevertheless what this marriage equality survey shows is that unconditional love always has the last word," he said.
Politicians are expected to begin discussing the specifics of the same-sex marriage bill as early as this week.
However, even ahead of the release of the results, conservative politicians inside the Australian parliament were preparing for a fight over how marriage equality would be legalized.
Prominent supporters of same-sex marriage celebrated the decision. Qantas CEO Alan Joyce danced on stage in Sydney with author and actor Magda Szubanski, and urged Turnbull to "get on with it."
Australian Olympic champion Ian Thorpe warned conservative politicians against delaying the legislation.
"(The result) spells it out loud and clear ... If they play around with this issue any longer, it will be at their peril," he told reporters Wednesday morning.
'We didn't want the vote'
Australia's LGBT community was strongly against the idea of a national vote on same-sex marriage from the first time it was announced, fearing a bitter, divisive campaign.
A group of same-sex marriage advocates even took the government to Australia's High Court in an attempt to stave off the survey. Their case was dismissed in an unanimous decision.
The two-month campaign was marred by harsh rhetoric and wild allegations of the consequences of a "yes" vote. Rainbow flags were sprayed with Nazi symbols in Brisbane
while "no" advertisements claimed same-sex marriage would lead to "radical gay sex" education in schools.
Speaking after the "yes" result on Wednesday, Jacob Holman, 28, and his husband Damien O'Meara, 29, said they still believed the survey was "wrong."
"We didn't want the vote in the first place but we are so happy to have this win for our friends and the whole community," Holman told CNN.
"The vote has helped to speed up the process but the true lesson here is that the process is wrong." Holman and O'Meara were married in Scotland two years ago.
Australians long in favor of marriage equality
Australians have long been in favor of marriage equality, but multiple governments have maintained they wanted to keep the traditional definition in law.
In 2015, under pressure from moderates in his Liberal party to take action, then-Prime Minister Tony Abbott announced there would be a national vote, or plebiscite, to decide whether marriage equality should be legislated.
He was unable to get funding to hold the plebiscite after legislation was blocked twice in the Australian senate. Abbott's successor, Turnbull, announced in August a national postal vote would be held.
It was one way to get around the funding issue, as the survey was run by the Australian Bureau of Statistics, removing the need for parliamentary approval.
Voting opened on September 12 and Australians who had registered to vote had until November 7 to return their surveys.
Developing story - more to come