A major No campaign group has conceded defeat in Ireland's historic abortion referendum after exit polls reported a landslide win for those advocating liberalisation.
Reformers said it was a moment of profound change, when the nation had collectively stood up for women and their healthcare.
Polling data suggesting seven out of 10 voters backed reform meant advocates for change were celebrating long before the first ballot boxes were opened at 9am on Saturday at count centres across the country.
The vote saw citizens effectively opt to either retain or repeal the Eighth Amendment of the state's constitution, which prohibits terminations unless a mother's life is in danger.
The Save the Eighth group said: "What Irish voters did yesterday is a tragedy of historic proportions.
"However, a wrong does not become right simply because a majority support it."
One poll by national broadcaster RTE suggested around 70% of the electorate have voted to end the country's all but blanket ban on terminations, with another, by The Irish Times, recording 68% in favour of ditching the prohibition.
While the official result is not due until later on Saturday, it appears Ireland is on the cusp of a defining moment in its social history.
The Together For Yes organisation said: "This is a vote for dignity and decency.
"If exit polls are reflected in the official vote count later today, this will be a moment of profound change in Ireland's social history, a moment when the nation collectively stood up for women and for their healthcare, and voted for constitutional change."
Reacting to the exit polls on Friday night, Taoiseach Leo Varadkar, a vocal proponent of liberalisation, tweeted: "It's looking like we will make history tomorrow."
Thousands of Irish citizens living overseas travelled home in droves to exercise their democratic right on the emotive issue.
The specific question people were asked was whether they wanted to see the Eighth Amendment replaced with wording in the constitution that would hand politicians the responsibility to set future laws on abortion, unhindered by constitutional strictures.
If the Yes vote is confirmed, the Irish Government intends to legislate by the end of the year to make it relatively easy for a woman to obtain the procedure in early pregnancy.
Ministers have promised to allow terminations within the first 12 weeks, subject to medical advice and a cooling-off period, and between 12 and 24 weeks in exceptional circumstances.
A total of 3.3 million citizens were registered to vote in Friday's referendum.
The Catholic Church was among influential voices calling for a No vote, arguing that the life of the unborn should be sacrosanct.
But the Yes camp, which portrayed itself as modernising and in step with international opinion, insisted repeal would demonstrate Ireland's compassion for thousands of Irish women forced to travel to England for the procedure.
A decade after the Eighth Amendment was approved, women in Ireland were officially given the right to travel abroad, mostly to the UK, to obtain terminations. Pro-repeal campaigners say almost 170,000 have done so.
The liberalisation campaign gathered momentum in 2012 after an Indian dentist, Savita Halappanavar, died in hospital in Galway aged 31 when she was refused an abortion during a miscarriage.
Her husband, Praveen Halappanavar, said she repeatedly asked for a termination but was refused because there was a foetal heartbeat.
In 2013, following an outcry over Mrs Halappanavar's death, legislation was amended to allow terminations under certain tightly restricted circumstances.
When doctors felt a woman's life was at risk due to complications from the pregnancy, or from suicide, they were permitted to carry out an abortion.
That did not sate the demand of pro-choice advocates.
Under pressure from the UN about alleged degrading treatment of women who travelled to England for terminations, the Irish Government began exploring the possibility of further reform, culminating in the calling of Friday's referendum and the promise to legislate.