An estimated 675,000 people lined the streets of Dublin for the annual St Patrick's Day parade, according to organisers.
The event, which included 2,000 performers and over 900 marching band members, was one of many taking place around the country - and across the globe - to mark the day.
The parade was led by four Grand Marshalls representing the four winning teams in the GAA Senior Cup Championships
The opening float was also a special tribute to the GAA to mark its 125th anniversary.
International participants included marching bands from the US, Germany and Canada, Bulgarian medieval masked dancers, and Spanish street theatre.
President Mary McAleese was in attendance, and the spectacle was broadcast live on RTÉ 1 television.
Parades were held in towns across the country, along with a range of other cultural events.
Gardaí estimated that 60,000 people turned up to watch Limerick's parade.
In Cork city, some 50,000 people watched the city's celebration.
The day is being celebrated around the world, particularly in the US, where New York's Empire State building will be lit up in green.