Australians will soon know whether an Indigenous voice will be enshrined in the constitution, as polls close across three states and the ACT.
Millions of voters attended 7000 polling booths across the nation on Saturday for the first referendum since 1999.
They were asked whether Aboriginal and Torres Strait Islanders should be recognised through a permanent, non-binding advisory body in the constitution that would be able to make representations to the government and parliament.
Polling closed at 6pm local time in NSW, Victoria, Tasmania and the ACT, with South Australia to follow, before polls close in Queensland, the Northern Territory and then finally Western Australia.
Four of the six states will need to vote in favour of the referendum for it to succeed on top of a majority of all Australia's voting 'yes'.
A three-three state tie will result in a 'no' result.
Prime Minister Anthony Albanese remained hopeful of a 'yes' outcome, despite published polls pointing to the 'no' vote succeeding.
Mr Albanese, who pledged the constitutional change in his 2022 post-election speech, said he had done everything possible to ensure a successful referendum.
"This is an opportunity for Australia to unite, to be strengthened by reaching out to our most vulnerable citizens," he said in his final pitch to voters on Saturday.
Mr Albanese said the 'no' campaign had "spoken about division while stoking it".
A Newspoll survey published in The Weekend Australian showed a three-point swing toward a 'yes' vote over the past week to 37 per cent.
With 57 per cent of surveyed voters saying they intended to vote 'no' as of Friday, a point down on the previous poll, the referendum would be lost if the poll results were reflected at the ballot box.
Six per cent of voters said they remained undecided.
Newspoll found there was not a single state where the 'yes' vote led.
When asked about the polls showing a victory for the 'no' vote, Indigenous Australians Minister Linda Burney she would work until the very last minute to convince people to vote for a better nation.
"It will mean so much to Aboriginal and Torres Strait Islanders," she told the ABC.
Prime Minister Anthony Albanese urged Australians to "show a generosity of spirit".
Opposition Leader Peter Dutton said the proposed advisory body was "risky, unknown, divisive and permanent".
He told Seven's Sunrise program he thought the voice would just be another layer of bureaucracy.
"If I thought it was going to provide the practical outcomes in Indigenous communities, then it would be a different story."
Nationals leader David Littleproud said the prime minister had divided the country and healing would now need to take place.
"In terms of the result, no one should feel guilty about how they vote today or guilt about the result," he told the ABC.
Labor frontbencher Michelle Rowland said the government would accept the decision no matter the outcome, but closing the Indigenous wellbeing gap remained a priority.
"We took to the election a commitment to have this referendum in our first term, we are honouring that commitment," she told Sky News.
But the 'no' campaign has been accused of dirty tactics on voting day, with a message by Fair Australia telling Australians: "don't risk a fine! Get to a polling place today and vote 'no' to the voice of division".
Greens senator Sarah Hanson-Young said the text messages were scaring people into voting 'no' and lodged a formal complaint with the Australian Electoral Commission.
"This is a sinister scare campaign and if it's not already illegal, it should be," she said.
Peter Dutton says Australians don't have enough detail on how the voice to parliament will work.
About 6.1 million Australians voted early and 2.1 million eligible voters applied for a postal ballot, leaving around 9.2 million Australians to cast their votes on Saturday.
Electoral commissioner Tom Rogers said he had been shocked at the "nutty" conspiracy theories surrounding the vote, with Australia having one of the most transparent voting systems in the world.