The former US president Mr Bill Clinton has arrived in Farranfore Aiport in Co Kerry at start of his four day visit to Ireland.
Mr Clinton is due to make a relaxed start to his trip with a round of golf at the prestigious Ballybunion links.
He is expected to spend the night at Dromoland Castle, Co Limerick, before two days of public engagements in Dublin.
Mr Clinton is to pay courtesy calls on the Taoiseach Mr Ahern and the President Mrs McAleese and will deliver this year's Trinity Lecture at Trinity College, Dublin.
The highlight of his trip to the capital is a celebrity-studded dinner in Dublin Castle on Tuesday, due to be attended by both Mr Ahern and Senator George Mitchell.
With seats at £10,000 a throw, the event will raise funds for the Northern Ireland Fund for Reconciliation.
Mr Clinton then heads North for a series of engagements.
President Clinton has played a pivotal behind-the-scenes role in the Northern Ireland peace process, paying an unprecedented three visits to Ireland during his eight years in office.
In November 1995, he became the first US president to visit Northern Island, with a tour taking in Dublin, Belfast and Derry.
He returned in September 1998 and a third time last December.
He made his first mark on the peace process in 1994 when he granted Sinn Féin president Mr Gerry Adams a 48-hour visa to visit New York - an IRA ceasefire followed seven months later.
Later that year, he appointed Senator Mitchell as special advisor on Northern Ireland, who later chaired the multi-party talks which led to the Belfast Agreement. PA