The Tánaiste's accompanying the President on the visit, and the Taoiseach will attend the State Banquet tonight.
The visit gets underway this morning when the Prince of Wales and the Duchess of Cornwall meet President and Mrs Higgins at the Irish Embassy.
They'll travel to Windsor for a ceremonial welcome by Queen Elizabeth and Prince Philip where the streets are lined with Irish tricolours and union flags, lunch in the Castle and viewing Irish items in the Royal collection.
An official tweet from the royal account last night welcomed the President and Sabina Higgins as gaeilge, with the hashtag Fáilte.
This afternoon he'll address a joint session of Parliament, before returning to Windsor and the State Banquet where he will address the gathering, as will Queen Elizabeth.
