More than 365,000 passengers are expected to travel through Dublin, Shannon and Cork airports over the weekend, according to Aer Rianta.
Up to 2,000 flights will arrive and depart over the long weekend including 350 charter flights, which have been added to the normal schedule.
As a result of All-Ireland clashes and festivals, Bus Éireann expects to carry 100,000 passengers over the holiday period.
Huge crowds have turned the Galway race festival into the country’s sporting mecca for the week as the Ballybrit venue proved a firm favourite for racing enthusiasts.
Now it’s the turn of Gaelic football, with four crucial championship games to be decided at Croke Park on Sunday and Monday.
Tens of thousands of fans from all parts of the country are due to converge on GAA headquarters for the All-Ireland extravaganza.
Down south, the 2003 Guinness Mitchelstown Music Festival features Australian diva Dannii Minogue as the headline act.
“I can’t wait for the gig,” said Dannii. “I have heard a lot about Cork and the great atmosphere there. I am really looking forward to it.”
All the fun is free, except for the Sunday afternoon concert with Dannii and other acts at the New Square venue where there is a 15 charge. The organisers expect a crowd of more than 40,000.
In Waterford, the 11th Spraoí, the city’s three-day streets jamboree, is expected to attract 80,000 people. There are more than 300 shows and performances both indoor and outdoor, to choose from.
Today also sees the opening of Féile 2003 in Belfast.
The nine-day West Belfast people’s festival draws fans from many countries for a mix of traditional and modern music and drama.
Over the next four days “the best of international queer cinema” is on view at the 11th Dublin Lesbian & Gay festival at the Irish Film Centre.