Counting is continuing after yesterday's referendum on the issue.
Christian, John Murray, director of the Iona Institute religious thinktank, one of the leading groups fighting the reform, accepted the result was going in favour of the reform.
"Obviously I'd be disappointed in that. We did our best to fight a good campaign and if having run that we haven't won it, we did our best," he said.
"Everyone is saying it is yes and I'm not going to argue with that."
Ballot boxes have been opened in 27 centres nationwide since 9am, but already many are certain of a Yes result in the Marriage Referendum.
On RTE, Minister for Health Leo Varadkar said it was a special day:"It seems to me that the Irish people had their minds made up on this some time ago," he said.
Before the vote, an alliance of evangelical Catholics and Protestants distributed more than 90,000 anti-gay marriage pamphlets in the last week across Ireland, urging the electorate to veto same-sex marriage.
They argued that the legalisation of gay marriage would undermine the Catholic faith and trigger unintended legal consequences in Irish courts, where adoption and surrogacy rights loom as distinct legal battlegrounds.
A yes provides fresh evidence of waning church influence in a country that, in the 1980s, voted forcefully in referendums to outlaw abortion and reject divorce.
Currently 17 countries, including the UK, Spain, France, Argentina and Denmark, along with several states in the US, allow same-sex couples to marry.
