The Queen is to pay a state visit to Ireland - the first official tour of the republic by a British monarch.
Buckingham Palace said in a statement: "The Queen has been pleased to accept an invitation from the President of Ireland to pay a state visit to Ireland this year. The Queen will be accompanied by the Duke of Edinburgh."
A date for the visit has not been released but it is widely expected to be in May.
The Queen will be following in the footsteps of her grandfather George V, who travelled to the country in 1911, before independence.
In a statement, the office of Irish president Mary McAleese said the timing of the visit would be confirmed at a later date.
"President McAleese is pleased to announce that Her Majesty Queen Elizabeth II has accepted an invitation to visit Ireland this year," it said.
"The dates of the visit and the programme will be announced jointly by Aras an Uachtarain (the president's residence) and Buckingham Palace in due course."
The Irish Government said it welcomed the imminent trip. "The visit will mark a further improvement in the very good relations between Ireland and the United Kingdom," it said in a statement.
After a meeting with Prime Minister David Cameron in London last June, outgoing Irish prime minister Brian Cowen said he wanted to see the official engagement before President McAleese leaves office after a second seven-year term in November.
Mr Cowen had said a state visit by the Queen and a return trip to Britain by an Irish president would be part of the normal courtesies enjoyed by friendly, neighbouring states.
