Hundreds of people will gather at Áras an Uachtaráin today to mark the anniversary of the Battle of the Boyne in 1690.
As thousands of Orangemen march through streets of Northern Ireland in commemoration parades, President Mary McAleese will hold a Twelfth of July garden party at her official residence in the Phoenix Park.
The event, the only State-funded celebration to mark the Twelfth in the Republic, is the tenth such reception to be held by the President.
Some 350 guests from all traditions and parts of the island will attend the party which will celebrate Williamite and Jacobite culture.
The event will feature entertainment provided by pipers from the Irish Defence Forces and members of the Corps of Drums 2nd Battalion The Princess of Wales' Royal Regiment, from Shackleton Barracks in Ballykelly, Derry.
Ulster-Scots and Irish dancers will also perform at the event.
