The first state visit to the Irish Republic by a British monarch is to made by the Queen later this year.
The historic announcement by Buckingham Palace is a hugely significant moment in the increasingly close relationship between Britain and Ireland.
Julian King, Britain's Ambassador to Ireland, said the Queen and the Duke of Edinburgh were very much looking forward to |the visit.
He added: “The invitation symbolises how far the relationship has come in recent years; the strength of our economic and |political ties; and the progress that has been made in Northern Ireland.
“The visit will provide an excellent opportunity to celebrate this, and build on the rich and varied links that exist across these |islands.”
A date for the trip has not been released but it is widely expected to be in May a few weeks after the wedding of Prince William and Kate Middleton.
Bobby McDonagh, Ireland's Ambassador to London, who delivered the Queen's invitation on behalf of President Mary McAleese, said: “The visit reflects the depth and the warmth of the British-Irish relationship and the extent to which it has developed in recent years.
“The friendship between our two islands and between our peoples has never been closer politically, economically or culturally.
“The visit will provide an excellent opportunity to celebrate what has been achieved, notably the successful and sustained peace in Northern Ireland which has been made possible by the close partnership between the British and Irish governments.”
The Queen's grandfather George V was the last monarch to
set foot on Irish soil when he visited in 1911.
His tour came 10 years before the country was |partitioned creating Northern |Ireland and the Irish Free State.
The bitterness caused by the move and the use of the British Army in the Troubles in Ulster strained relations on both sides of the Irish Sea for much of the |20th century.
The Queen also suffered her own personal loss when her cousin Lord Louis Mountbatten was killed by an IRA bomb blast which tore apart his boat in |Ireland in 1979.
But the success of the peace process has greatly eased tensions and ultimately led to the planned visit being able to take place. Britain's close ties with the |Republic saw it contribute about £7bn to the bailout package for the country's economy following the spectacular collapse of the Celtic Tiger boom during the worldwide economic downturn.
Rumours of the visit have been circulating for more than a year with the official announcement widely anticipated.
But it has drawn criticism from Sinn Fein president Gerry Adams who said his party believed|the visit was premature, but claimed it was an indication of a changed time.
But SDLP leader Margaret Ritchie has welcomed the |announcement.
She described it as sign of the positive maturity and closeness |of Anglo-Irish relations in |recent times.
The last visit to Ireland by a British King or Queen was in 1911, when King George V and Queen Mary arrived with two of their children, Princess Mary and the future Edward VIII. For the next 84 years any royal visits to what became the Republic were conducted in private. A visit by Prince Charles in 1995 was marred by violent demonstrations by republican groups. Protesters threw potatoes (in memory of the Famine), and there were also demonstrations against his role as colonel-in-chief of the Parachute Regiment. Relations with Britain have become somewhat normalised since the Good Friday Agreement, but the now 86-year-old monarch's visit will be the |ultimate test of any relationship between the two countries.