The Duchy of Lithuania (Latin: Ducatus Lithuaniae; Lithuanian: Lietuvos kunigaikštystė) was a state-territorial formation of ethnic Lithuanians which existed from the 13th century to 1413. For most of its existence, it was a constituent part and a nucleus of the Grand Duchy of Lithuania. Other alternative names of the territorial formation, used in different periods, were Aukštaitija or Land of Lithuania (13th century), Duchy of Vilnius (14th – early 15th centuries), Lithuania proper or simply Lithuania (in a narrow sense).