The Grand Duchy of Oldenburg was a grand duchy within the German Confederation, North German Confederation and German Empire that consisted of three widely separated territories: Oldenburg, Eutin and Birkenfeld. It ranked tenth among the German states and had one vote in the Bundesrat and three members in the Reichstag.

A grand duchy is a country or territory whose official head of state or ruler is a monarch bearing the title of grand duke or grand duchess.