Luxembourg is a grand duchy.
Luxembourg [ ˈlətsəbuərx ] Luxemburg ) , officially the Grand Duchy of Luxembourg , is a landlocked country in western Europe . As a representative democracy with a constitutional monarch , it is headed by a Grand Duke , Henri , Grand Duke of Luxembourg , and is the world 's only remaining grand duchy . The Grand-Duchy , with its powerful fortress , became an independent state under the personal possession of William I of the Netherlands with a Prussian garrison to guard the city against another invasion from France .