King Charles III will be in the province, meeting the political leaders and the public.
A service of reflection on the life of the Queen will be held at St Anne’s Cathedral.
Members of the public will have opportunities to see the king and queen consort in both Royal Hillsborough and in Belfast city centre.
It is a sombre occasion, and also one of the most high-profile royal visits in the 101-year history of Northern Ireland.
The visit by the great-grandfather of the current king, George V, was a short one but it in effect set the seal on the very existence of NI.
Other striking visits include that of the late Queen’s father, George VI, in 1942, when World War Two was raging, and when the powers that be had, a year before, failed to realise that Ulster was within reach of German bombers.
Also the visit by George VI in 1945, when that existential fight against the Nazis was resolved in the Allies’ favour.
The Queen’s first visit here, after she inherited the crown in 1952, was memorable and her silver jubilee journey to NI on board Royal Yacht Britannia in 1977 was of lasting symbolism, showing that years of terrorism would not cause a part of the UK to become out of bounds to its head of state.
Recent days have helped to shine light on how the nation operates. The king addressed parliamentarians, who have almost complete power to the monarch’s almost none. And yet the system, of a hereditary constitutional head of state who takes no political decisions, while one that almost no-one would devise from scratch, works.
And it is the powerless king or queen who is typically more popular than politicians who have actual authority.
Today people across NI will be remembering a Queen who came here many times, and reflecting on events, as is the theme of the service at St Anne’s.