Turnout at polling stations in the fiscal treaty referendum was low throughout the country.
Estimates suggest only half of the 3.13 million people eligible to vote in the referendum did so.
The counting of votes begins at 9am tomorrow.
This morning, President Michael D Higgins cast his first vote as head of State, along with his wife Sabina, at St Mary's Hospital in the Phoenix Park.
Also voting early were many of the leading campaigners on either side. Taoiseach Enda Kenny was at St Patrick's National School in Castlebar, while Sinn Féin leader Gerry Adams voted at Dulargy National School, in Ravensdale, Co Louth.
Tánaiste Eamon Gilmore voted at Scoil Mhuire in Shankill, while in the same constituency Richard Boyd Barrett of the United Left Alliance was at Harold National School in Glasthule.
Fianna Fáil leader Micheál Martin was at St Anthony's National School in Ballinlough, Co Cork, and Independent Finian McGrath voted at Scoil Mhuire at Griffith Avenue in Dublin.
It is the ninth Europe-related referendum and the 33rd time the electorate has been asked to approve a change in the 1937 Constitution.
In the last comparable referendum on the Lisbon Treaty the turnout was 59%.
Islanders and those in institutional care have already cast their ballot, while a further 13,000 are eligible for postal votes.