More than 500,000 people turned out to watch the St Patrick's Day parades around the country, though cold weather meant that attendances were down on last year.
Some 400,000 people lined the streets of Dublin to watch more than 2,000 participants from Ireland and the United States as well as groups from Togo, Bangladesh and Shanghai march through the city.
More than 50,000 people turned out to watch the parade in Cork, some 55,000 in Galway, approximately 30,000 in Limerick and about 30,000 in Waterford.
An estimated 5,000 attended a parade and concert in Belfast, where the parade was officially recognised by the City Council for the first time.
Millions of people around the world also joined in the celebrations. In New York, two million people attended the city's two hundred and forty fifth Patrick's Day parade. Hundreds of other cities including Sydney and Singapore marked the event with street festivals and parades.
President's St Patrick's Day message
The President, Mary McAleese, said St Patrick's Day is a one off celebration for Irish people and their friends at home and abroad.
The President said the Ireland of today was vibrant, cosmopolitan and filled with energy and that international relations were playing an important part in our maturing as a nation.
Meanwhile, the Catholic Primate, Archbishop Seán Brady has warned against celebrating St Patrick without referring to his Christian faith.
In his message for the national feast day, Archbishop Brady says today unites Irish people everywhere and that the national saint has become a symbol of Irish history and heritage.
However, the Archbishop of Armagh warns that simply reducing St Patrick to this without referring to his Christian faith distorts the truth.
Few arrests throughout the country
Gardaí reported a mainly quiet day throughout the country. 33 people have been arrested since this morning by gardaí from Pearse St station in Dublin.
Gardaí say most of the arrests were for minor public order offences. However, gardaí say overall the situation in the city centre has remained calm throughout the day.
Gardaí in Store St station in Dublin city say the security situation in the north inner city has also remained very quiet and calm, and there are no reports of any arrests there.
Gardaí in Cork City say they have arrested 15 people since 2pm this afternoon, again mainly for public order offences.
Galway gardaí say they have had "a few arrests", but the situation overall is much quieter than last year.
And in Limerick, gardaí say approximately 12 people have been arrested for public order and theft offences.
