The Marriage Act 2015 has been signed into law, and the move has been praised across the globe.
The Presidential Commission signed the act into law last night.
It now needs a commencement order from the Minister for Justice Frances Fitzgerald which, once signed, will allow same-sex marriages to begin within weeks.
Director of the Gay and Lesbian Equality Network (GLEN) Brian Sheehan said we now had a more inclusive society, adding: "The moment in Dublin Castle when the result was declared and the crowds sang Amhrán na bhFiann was the moment we realised belonged to Ireland in a very special way.
"It's a quiet moment for all of us to feel we now fully belong in Ireland."