Queen Elizabeth II is to pay a state visit to Ireland this year - the first ever by a British monarch since Irish independence in 1921, Buckingham Palace said Friday.
The queen, who will be accompanied by the Duke of Edinburgh, accepted an invitation from Irish President Mary McAleese, dpa reported.
The queen's grandfather, King George V, was the last monarch to visit the country in 1911, before Irish independence.
There was no official date set for the visit, but it is expected to be in May.
The Republic of Ireland gained independence from the British crown in 1921, with Northern Ireland alone remaining a part of the United Kingdom.
The use of British forces in the bloody violence in Northern Ireland, known by both sides colloquially as The Troubles, strained relations for most of the 20th century.
One of the earliest events in the Troubles was "Bloody Sunday," January 30, 1972, when British soldiers policing a civil rights march in Londonderry shot dead 14 Catholic civilians.
From that point, mutual attacks by the Irish Republican Army (IRA) and Protestant paramilitary groups such as the Ulster Defence Force (UDF) turned the province into something at times approaching a war zone - with IRA bomb attacks on mainland Britain too.
In 1979, the queen's cousin, Lord Louis Mountbatten, was killed by an IRA bomb blast on his boat in Ireland.
The political wing of the IRA, Sinn Fein, finally entered into talks with the British government, leading to the Good Friday Agreement of 1998.
The success of the peace process in Northern Ireland has eased tensions between the two nations.