Ireland will begin counting around two million votes that will determine the make-up of its new government - if one can be formed at all.
In one of the country's most uncertain general elections in recent times, an exit poll suggests a massive slump in support for the outgoing Fine Gael/Labour coalition.
Fianna Fail, Sinn Fein, Independents and smaller parties all made significant gains, according to the survey of people leaving polling stations by pollsters Ipsos MRBI for the Irish Times.
The poll shows Fine Gael on 26.1% of first preference votes; Labour on 7.8%; Fianna Fail on 22.9%; Sinn Fein on 14.9%; Anti Austerity Alliance/People Before Profit on 3.6%; Greens on 3.5%; Social Democrats on 2.8%; Renua on 2.6%; and others on 16.1%.
However the figures come with a health warning, given Ireland's unusual and complex single transferable vote system.
As polling stations closed at 10pm on Friday, political parties were estimating around two thirds of the 3.3 million-strong electorate voted.
Turnout was uneven across the regions with booths in rain-sodden parts of Cork and Waterford much less busy than other areas during the day.
Reports also suggest that turnout in urban areas was down on the 2011 general election, when it was 70% nationally.
Opinion polls have been showing for months an electorate increasingly turning away from mainstream parties to smaller factions and Independents.
A hung parliament is widely predicted with the voter schism also threatening to blow apart a duopoly enjoyed for more than 80 years by Fine Gael and Fianna Fail, which swapped power for generations.
Despite ruling each other out as potential bedfellows, in a "grand coalition" that would bring to an end a bitter rivalry since Ireland's civil war, the unlikely union has been hotly-tipped by pollsters and pundits as the odds-on favourite outcome.
Such a ground-breaking shift could also open a definitive right/left divide in Ireland's parliament, the Dail, for the first time since the foundation of the state.
After five years of bruising austerity, Labour would need to defy widely-held predictions of big losses at the ballot box to help make up the numbers with its former senior coalition partners.
Other possibilities include a minority Fine Gael government, supported by arch-enemy Fianna Fail, or a rainbow coalition of Fine Gael, Labour and some smaller parties.
Once a clear picture emerges from the weekend counting of votes, the parties will have until March 10 - when the Dail is scheduled to resume - to forge a power-sharing deal.
The spectre of a second election will loom over any uncertainty.
Despite being the shortest general election campaign in Irish political history, it was a drawn-out, lacklustre three weeks that generally failed to ignite the imagination of the population.
More than 550 candidates are fighting in 40 constituencies for just 158 Dail seats.
With eight fewer seats than last time around, the competition will be particularly intense in some constituencies who are down a representative.
Islanders off the coasts of Donegal, Mayo and Galway voted on Thursday to make sure their ballots were back in time for the count.
President Michael D Higgins and leading politicians were among the first to cast their votes as the polls opened nationally on Friday just before sunrise.