An estimated 5,000 people have marched in Dublin city centre calling on the Government to extend marriage rights to same-sex couples.
Civil partnership was introduced in Ireland two years ago. It gives same-sex couples rights that are similar but not equal to those of heterosexual married couples.
Gay marriage was recently legalised in England, Wales and France. Recent polls suggest up to three-quarters of people would support similar legislation in Ireland. Recognising same-sex marriage would require an amendment to the Constitution.
In April, the constitutional convention voted overwhelmingly in favour of extending marriage rights to same-sex couples. The Cabinet is expected to make a formal response to the proposal in October.
Tánaiste Eamon Gilmore has indicated there will be a referendum on the issue in 2014.