Northern Ireland was a country situated on the island of Ireland. It was one of four countries in the United Kingdom, in addition to those of Great Britain.
In 1879, Victoria was Queen of the "United Kingdom of Great Britain and Ireland." (TV: Tooth and Claw) Later, the nation was known as the "United Kingdom of Britain and Northern Ireland", as stated by the Eleventh Doctor (TV: The Beast Below) while John Frobisher, in 2009, identified himself as Permanent Secretary to the Home Office of "the United Kingdom and Northern Ireland." (TV: Children of Earth: Day Three)
Monaghan, located in Northern Ireland, was the birthplace of Michael Gibney. (PROSE: The Lost Skin)
During the 1970s, the Irish Republican Army was active in Northern Ireland. (PROSE: Who Killed Kennedy)
It was still a part of the UK in the 33rd century, when the British population bar Scotland inhabited Starship UK. (TV: The Beast Below)