The Republic of Ireland has voted overwhelmingly to overturn the abortion ban by 66.4% to 33.6%.
A referendum held on Friday resulted in a landslide win for the repeal side.
Currently, abortion is only allowed when a woman’s life is at risk, but not in cases of rape, incest or fatal foetal abnormality.
The Eighth Amendment, which grants an equal right to life to the mother and unborn, will be replaced.
The declaration was made at at Dublin Castle at 18:13 local time.
The only constituency to vote against repealing the Eight amendment was Donegal, with 51.9% voting against the change.
A vote in favour of repeal paves the way for the Dáil (Irish Parliament) to legislate for change which would see the introduction of a much more liberal regime.
Ireland’s time of reckoning
The people travelling #HomeToVote
Timeline: Ireland and abortion
Live coverage: Referendum results
Reacting to early indications of the result, the taoiseach (prime minister) who campaigned in favour of liberalisation, said: “What we’ve seen is the culmination of a quiet revolution that’s been taking place in Ireland over the past 20 years.”
Leo Varadkar added that Irish voters “trust and respect women to make the right choices and decisions about their own healthcare”.
Mr Varadkar said he hoped to have a new abortion law enacted by the end of this year.
At the scene: Kelly-Leigh Cooper, BBC News
The people behind the Repeal campaign were always hopeful of a positive outcome today – but no can quite believe they have received such a resounding Yes from the Irish public.
Tears streamed as they watched the poll predictions come true throughout Saturday.
For those who have campaigned tirelessly and helped women in crisis for years – this moment is long overdue.
A celebratory atmosphere has swept across much of the Irish capital. It’s impossible to avoid Repeal jumpers and Yes stickers worn proudly on chests everywhere.
Many supporters gathered at the castle (the same place the same-sex marriage results were welcomed three years ago) to celebrate together as results rolled in.
Hugs are being given and cheers of “Yes, yes yes,” are filling the air.
‘Continue to protest’
Counting began at 09:00.
After the polls were published, one of the main anti-abortion campaigns conceded it had lost the vote.
The Save The 8th campaign described the result as a “tragedy of historic proportions”.
“The unborn child no longer has a right to life recognised by the Irish state,” said its spokesman John McGuirk.
However, he vowed that No campaigners would continue to protest, “if and when abortion clinics are opened in Ireland”.
The leader of the main Irish opposition party, Micheál Martin of Fianna Fáil, said the vote was the “dawn of a new era”.
Sinn Féin president Mary Lou McDonald, whose party campaigned in favour of a Yes vote, said: “We have without doubt done right by Irish women for this generation and many to come.”
Amnesty International hailed the result as a “momentous win for women’s rights” that “marks the beginning of a new Ireland”.
Northern Ireland’s abortion laws
The vote will have repercussions for women north of the border, as Northern Ireland has the strictest abortion laws in the UK.
Cases of rape, incest and fatal foetal abnormality are not considered grounds for a legal termination.
The UK’s Women and Equalities Minister Penny Mordaunt said the predicted landslide vote gave “hope” to Northern Ireland.
“We cannot be left behind in a corner of the UK and on the island of Ireland as second-class citizens.”
Former Northern Ireland health minister Jim Wells said the expected result was a “grave threat” to the unborn child in Northern Ireland.
Mr Wells, a Democratic Unionist Party (DUP) politician, claimed it was “inevitable” that abortion clinics would be set up in border towns to “promote their services to Northern Ireland women”.
“It will be much easier to terminate a child’s life if this can be done at a clinic in Dundalk or Letterkenny rather than flying to London or Manchester,” he added.