The proposed United Baltic Duchy^[1] also known as the Grand Duchy of Livonia^[2] was a state proposed by the Baltic German nobility and exiled Russian nobility ^[3] after the Russian revolution and German occupation of the Courland, Livonian and Estonian governorates of the Russian Empire.

The idea comprised the lands in Estonia, Latvia, Lithuania, and Belarus and included the creation of a Duchy of Courland and a Duchy of Estonia and Livonia that would be in personal union with the Crown of Prussia ^[4] under the German Empire's occupied territory Ober Ost before the end of World War I covering the territories of the Medieval Livonia what are now Latvia and Estonia.