The United Kingdom (UK) is arguably Europe's most influential country. In simple terms, it's the union of the individual countries of England, Scotland and Wales, collectively called Great Britain (Europe's largest island) and the northeastern corner of Ireland - the constitutionally distinct region of Northern Ireland.
The United Kingdom is a constitutional monarchy. Its reigning monarch, Queen Elizabeth II, is also the Queen and Head of State of (15) other Commonwealth realms, including Australia, Canada, Jamaica and New Zealand.
Despite the decline of the British Empire, the United Kingdom remains a consequential force; it's the fifth largest economy in the world, second largest in Europe, and a respected military power.