More than three million people are eligible to vote
There has been a steady stream of voters casting ballots around the country in the Eighth Amendment referendum.
The polls opened at 7.00am and will close at 10.00pm.
More than three million people are eligible to vote in the first referendum on the Eighth Amendment in 35 years.
Earlier the Referendum Commission chairperson urged voters to 'make sure their voice is heard' on polling day.
Ms Justice Isobel Kennedy had some straightforward advice for voters.
"The important thing to do today is to decide when you are going to vote and then to vote," she said.
"Polling stations are open form 7.00am until 10.00pm.
"Our message is simple; the debate is over and now everyone should make sure their voice is heard."
Political leaders were out in force earlier.
An Taoiseach Leo Varadkar earlier voted in Scoil Thomas Lauriel Lodge in Castleknock.
While Sinn Féin President Mary Lou McDonald cast her vote on the Navan Road in Cabra.
Voters will be asked a Yes / No question in the ballot box.
A ‘Yes’ vote would see Article 40.3.3 removed from the Constitution and allow the Oireachtas to introduce laws governing abortion.
A ‘No’ vote would see the Eighth Amendment retained as it is now, with Ireland’s laws against abortion remaining in place.
These people were out voting early this morning:
You should mark an 'X' next to your choice.
Do not write anything else on the card as it could be seen as a spoiled vote.
Your voting card will tell you where your polling station is.
If you have not got a voting card, you can still vote as long as you are on the register of electors.
In that case, bring your ID to the centre to be allowed to vote.
No videos or photos - including selfies - can be taken in the polling station.
You also should not wear any jumpers, badges or merchandise promoting either side when you go to the station to vote.
Thousands of Irish people living abroad have travelled home to vote - with the hashtag trending all over social media.
People from both sides of the debate are making their way to local polling stations from as far away as Australia to have their say.
One Twitter user reported a woman handing out Tayto crisps at Dublin Airport to people at the arrival gates.