Taoiseach Bertie Ahern will address a joint session of the House of Commons and the House of Lords at Westminster tomorrow.
The invitation to speak to members of the House of Commons and the House of Lords is one rarely offered to foreign leaders.
Up to 100 other guests, including Fine Gael leader Enda Kenny, will attend the event in the Royal Gallery shortly after noon.
Mr Ahern, accompanied by British prime minister Tony Blair, will enter the Royal Gallery through the Sovereign's Gate - the entrance used annually by Queen Elizabeth.
The two men will be accompanied by the speaker of the House of Commons, Glasgow MP Michael Martin, and the speaker of the House of Lords, Baroness Hayman.
Mr Ahern's address will deal with the transformation that has taken place in the relationship between Ireland and Britain.
The Royal Gallery last week hosted a similar joint session of both houses of parliament to honour the former secretary general of the United Nations, Kofi Annan.
The outgoing French president, Jacques Chirac, has also been granted the honour, as has the former president of South Africa and ANC leader, Nelson Mandela.