The public decided by a two-to-one landslide to repeal part of the state’s constitution which effectively prohibits terminations unless a mother’s life is endangered.
A referendum was held on Friday and produced overwhelming consensus for reform amongst men and women, nearly all classes and age groups, and across most counties in Ireland.
Taoiseach Leo Varadkar hailed the culmination of a “quiet revolution” and said a new law could be in place before the end of the year.
Referendum returning officer Barry Ryan said a majority of more than 700,000 voted Yes to repeal.
About two million people voted and results showed urban dwellers and a significant proportion of rural voters backed repeal of the Eighth Amendment of the constitution.
In parts of Dublin almost 80% favoured liberalising restrictions on abortion in early pregnancy.
About 170,000 Irish women have travelled to the UK and other places for the procedure since 1980.
Pollsters suggested the stories of women forced to travel or take illegal pills obtained on the internet helped sway public opinion, as well as the death of an Indian dentist denied the procedure while she miscarried.
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.
Mr Varadkar said the result represented “the culmination of a quiet revolution”, one that had been taking place in Ireland for the past 10 to 20 years.