Voting in the Presidential Election gets under way from 7am with the polls remaining open until 10pm tonight.
The vote is taking place at more than 5,500 polling stations across the country.
Some 3.6 million people are eligible to vote today.
Given that it is a secret ballot, the taking of selfies or pictures, that reveal who a person voted for, can lead to prosecution.
People do not need their polling cards but it is viewed as helpful to bring it to the polling station.
However, a passport, public service card, driving licence or bank cards with proof of address will suffice.
Pencils are available at all polling stations but people can bring their own pen or pencil if they wish.
In this election, three candidates were validly nominated.
Unusually, Fianna Fáil's Jim Gavin stepped aside during the contest.
His name remains on the ballot paper, along with Fine Gael's Heather Humphreys and Independent Catherine Connolly, because he withdrew after the close of nominations.
Therefore any votes for Mr Gavin will be counted and distributed in the usual way.
Boxes will be opened at 9am tomorrow when the counting of votes begins.
