Michel Barnier will spend two days touring the Republic, which will be more affected by Britain leaving the EU than any other member state.
He has been invited to talk to both houses of the Irish parliament – a rare honour usually reserved for visiting heads of state including Nelson Mandela and Bill Clinton.
In fact the honour is so rare Ireland’s own president has not addressed both houses in the 21st century.
This address by the high-ranking EU official carries extra weight given the perceived snub by Prime Minister Theresa May earlier this year.
She was given the rare opportunity of speaking at the Irish parliament to address the litany of concerns facing the island after Brexit but refused – a move seen as insulting by many within the bloc.
During his visit Mr Barnier will also visit the Irish border, which is a major cause for concern on the island but was all-but ignored during the Brexit referendum.
The creation of a hard border risks re-igniting tensions and violence in the north of the island, which is still scarred by the 3,500 killings during the Troubles.
While Mrs May has given lukewarm assurances a return to Troubles-era checks and stops will not occurr, she has failed to explain how this will be possible when it will become the only land border between the EU and the UK after Brexit.
Mr Barnier has promised to address these issues, as well as those relating to free movement of people and trade between the two states.
He will also meet Taoiseach Enda Kenny during his visit, who is currently under pressure to resign as leader of the country.
Mr Barnier’s visit also comes as Tony Blair visits the country, where he is to address the get together of centre-right, pro-European parties from 40 countries on Friday.