There is a country called the United Kingdom.
United Kingdom . It is also the 21st-most populous country , with an estimated 65.1 million inhabitants . Together , this makes it the fourth-most densely populated country in the European Union ( EU ) . The United Kingdom is a developed country and has the world 's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity . It was the world 's first industrialised country and the world 's foremost power during the 19th and early 20th centuries .