New Zealand will become just the seventh country in the world to legalise euthanasia after voters overwhelmingly backed the right to die in a binding referendum.
The margin of support - 65.2 per cent to 33.8 per cent against - means the outcome cannot be overturned by the 480,000 special votes which are still to be counted.
As a result, the End of Life Choice Act will come into force on November 6, 2021 - a year after official results are announced next week.
"The country has decided to support compassion and choice," said Act party leader David Seymour, who sponsored the historic law change.
He celebrated the margin of support - nearly two votes to one - saying it gave a strong mandate for legalising voluntary euthanasia.
"What a great day to be a Kiwi," he told a crowd gathered to celebrate the result at Parliament.
Seymour paid tribute to Wellington lawyer Lecretia Seales, whose unsuccessful court challenge to get access to assisted dying in her dying days inspired him to draft the End of Life Choice Act.
"I never met Lecretia and I really wish I had. To go to court with a cancer in your brain takes a steely determination that few of us have.
"We've very lucky as a country that we have Lecretia."
Seales' mother, Shirley, described the referendum result as a relief.
"Tears have been flowing down my face," she told the Herald.
"I was too scared to think that it was going to go our way and it was such a majority we wouldn't have to wait till next week to have it confirmed - so it was such a big relief.
"Lecretia would have been so happy that it's finally come to fruition, she would have been over the moon. I am bursting at the seams with pride that she was part of this.
"She would have been so blown away that so many people have acknowledged her for the part she played."
After the results were announced, Prime Minister Jacinda Ardern confirmed she voted "yes" in the euthanasia referendum and said her Government would progress the legislation in line with the will of the people.
The result rattled euthanasia opponents, who said the law change would be harmful to New Zealand's most vulnerable people.
Salvation Army territorial commander Mark Campbell said he was "extremely concerned" that assisted dying would become legal in this country.
"We believe many New Zealanders are unaware of the lack of safeguards contained within the End of Life Choice Act and that vulnerable people, such as the elderly and those struggling with mental illness, will be especially at risk from this law.
He added: "The Salvation Army calls on the Government to increase funding to enable more people to access New Zealand's world-renowned palliative care system. We believe that, with adequate access to high-quality end-of-life care, vulnerable people can be supported through their illness and dying, and will not feel pressured into euthanasia."
The referendum result brings to an end a five-year process since Seymour placed the End of Life Choice Bill in the private members' ballot. It was pulled from the ballot in mid-2017 and was passed by Parliament in 2019 - before being put to the public in the referendum.
Public support for voluntary euthanasia has been consistently strong for the past 20 years, with most polls between 60 and 70 per cent in favour.
But legalisation is still a radical act in international terms. Only six countries and a handful of United States and Australian states have legalised assisted dying or euthanasia.
The result caused anxiety among parts of the disabled community today. Although the law forbids access to euthanasia on the grounds of disability alone, advocates feel it fundamentally changes the way vulnerable people will be perceived in New Zealand.
There are also concerns that the law's relatively narrow eligibility criteria could be broadened in future.
"I am pretty gutted," said disability advocate Dr John Fox, who has a painful neuromuscular condition called spastic hemiplegia.
"Instead of improving palliative care and addressing any of the underlying issues we've opted to assist people to commit suicide," he said.
Fox said the referendum showed "a shameful misordering of priorities" and "changed New Zealand's moral and social fabric in a permanent way".
He said advocates would now redouble their efforts to ensure lives were not put at risk by the legislation, and that palliative and pain relief services were adequate.
Asked for his message to those who were fearful of a law change, Seymour said: "I can assure people this bill is watertight. If anything it may be a little too rigorous.
"The evidence around the world is that there is nothing to fear from the kinds of arguments that people put up."