At least 60,000 people are expected to attend the Dublin Pride Parade this afternoon.
It starts in O'Connell Street at 1pm, before making its way on to Eden Quay and Liberty Hall.
It has been held since 1983, when the first big march for gay rights took place in Ireland.
The GAA, along with civil and public servants, are taking part for the first time today.
Neil Ward, from the Department of Justice, says it is a historic day.
"It's incredibly important. LGBT staff work in all areas of the public service," said Mr Ward.
"And today we get to show that publically for the first time.
"650 people from across every single government department, the gardaí. the defence forces, prison officers and many other public bodies are going to march together and show that we're proud to work for Ireland."