Celebrations are ongoing at the Galway West count centre, where 66% of voters voted to repeal the 8th Amendment.
42,422 voted Yes, while there were 21,906 No votes.
The two-to-one vote in Galway West means that all three Galway constituencies voted Yes.
Galway West voted 64.5% in favour of the 8th amendment in 1983 and 61.4% said yes to marriage equality in 2015.
Nationally, Donegal looks set to be the only county to have voted No. People aged over 65 voted No, while the exit polls showed that 88% of 18 to 24-year-olds voted Yes.
Earlier, Galway East was the first result in the country to come through, with a 60% Yes vote.
