Thousands of Irish ex-pats from across the world are returning home to vote 'Yes' in a referendum on whether to legalise gay marriage.
Under the Twitter hashtag #HometoVote, travellers are recording their journeys back to Ireland.
Polls on Friday indicate that the referendum will be passed by a margin of as much as 2 to 1, which would make the country the first in the world to adopt the policy by popular vote.
Responding to calls from the Get the Boat to Vote campaign, London's Euston Station was reportedly busier than usual with Irish citizens returning home to cast their ballot.
Among those responding to the "we're coming home campaign", which called on Irish nationals living further abroad to return for the referendum, was actress Saoirse Ronan.
The policy is backed by all of the country's main political parties, and opposed by Catholic Church groups.
With Ireland one of only three countries in Europe that does not allow votes to be cast by post, those casting a ballot in the referendum have to do so in person.
Only Irish nationals who left the country in the last 18 months are eligible to vote, which is more than 60,000 voters, a significant number in a country with 4.95 million citizens.
Voters are being asked whether an article should be added to the country's constitution saying: "Marriage may be contracted in accordance with law by two persons without distinction as to their sex."
Polling stations around the country opened at 7am BST, and will close at 10pm, with the result to follow on Saturday.
The once deeply Catholic country only legalised homosexuality in 1993.
In his final live televised interview ahead of the opening of polling stations, Ireland's prime minister, Enda Kenny, urged voters to vote yes "for love and for equality".
Paddy Monaghan, one of the co-ordinators of the religious groups campaigning for a no vote said: "If there is a yes vote, will the Muslim printer in Ireland now be obliged to print cartoons of Muhammad? Redefining marriage is sold to us by the media and political establishment as a permissive measure but it will quickly become coercive."
Referendums on gay marriage held in Slovenia and Croatia have both resulted in 'no' votes.