The President, Mrs McAleese, has called for St Patrick's "ethos of respectful tolerance" to continue to inspire Irish people as they face new social challenges and opportunities.
In a message to be read at celebratory events throughout the world today, Mrs McAleese says in the saint's life and work, "we can trace so much that remains fresh and relevant for Ireland today, not least his capacity to accept difference, indeed to embrace and celebrate it".
The President and her family will lead the attendance at the main parade in Dublin today.
In her address, she notes: "Patrick came to Ireland, a stranger from a foreign land. He had no capital but his faith in God, faith in himself, a profound love of humanity and his determination to make a difference . . . His journey was far from easy and many an Irish emigrant has drawn hope and comfort from his experience".
Before the parade, the President will attend 10 a.m. Mass at the Pro-Cathedral. In the afternoon, she will host a reception at Aras an Uachtarain for over 100 guests including church leaders, members of the Council of State and representatives of Government Departments and the new North-South cross-Border bodies.
Pre-parade entertainment begins in the capital at 10.30 a.m. with fire-jugglers, clowns and magicians as well as a vintage car rally.
The official start will be heralded by the arrival of the Lord Mayor of Dublin, Ms Mary Freehill, in a horse-drawn coach followed by the No 1 Army Band and the parade's grand marshal, actress Pauline McLynn.
Among the highlights are "The Puca", an inflatable sea-horse made by the Blow Ins performance group in Ballyvaughan, Co Clare and "Krakaboom", an explosion of medieval chaos by the Waterford Spraoi group.
Keeping closely to the parade theme "Hullabaloo", the Wexford theatre group Bui Bolg have created a fictional city with citizens and a mayor of Hullabaloo, all making a noise of some sort.
The Minister for Tourism, Sport and Recreation, Dr McDaid, will attend the event before flying to Paris tonight where, he said, he intends to invite expats to consider returning home to fill jobs vacancies here.
Other festival events in Dublin today are the RTE Monster Ceili in St Stephen's Green, and a funfair on both sides of the Liffey.
Temple Bar will also be the centre of much attention as the TV presenter Chris Evans broadcasts a St Patrick's Day edition of his show TFI Friday from Eamonn Doran's.
Guests are expected to include celebrity couple Puff Daddy and Jennifer Lopez, the Corrs and Bono, who tomorrow will receive the freedom of the city with the other members of U2 at a ceremony in Smithfield.
Extensive traffic restrictions will be in operation throughout Dublin, with streets on the parade route closing from 7.30 a.m. today. Parking meters will not be in use and clamping will be suspended. However, cars illegally parked or causing an obstruction will be towed away.
Dublin Bus is operating a Sunday service with extra buses this morning. There will be additional DART trains during the parade, but delays are expected and, as a safety measure, Tara Street station will be closed until 6 p.m.
AA Roadwatch has warned of traffic delays on some main routes, including the N11 at Bray, where a parade takes place between 3 p.m. and 5 p.m. Parades in Arklow, Gorey, Enniscorthy, Wexford, Portlaoise and Roscrea were cited as likely causes of traffic disruption.
Among those heading to overseas events yesterday were 75 people from Dublin, Clare, Westmeath, Sligo and Cork, who are to attend a parade in the Belarussian capital of Minsk today. The group, which is part of the Chernobyl Children's Appeal Ireland, will distribute supplies to orphanages.
