The Duchy of Alšėnai (Lithuanian: Alšėnų kunigaikštystė) was a feudal patrimony of the Alšėniškiai in the late 13th and mid-16th centuries.
It was first mentioned in the Bychowiec Chronicle, where Alšis [lt], son of Romuntas [lt] (slavicized as Holsza, son of Romunt), according to legend, was the one who "founded a town on the river Korablis; He arose from there, began reigning and called himself the duke of Alšėnai".
[1] Maciej Stryjkowski also relates the origins of the Alšėniškiai family to Alšis Romuntavičius (c. 1250), coming from the line of Dausprungas.
[2] The dukes of Alšėnai held high positions in the Lithuanian state for a long time.
In the 15th century, the duchy stretched from north to south - from Vilkmergė (now Ukmergė) and Pastavy to Hlusk and Turov, from east to west - from Minsk to Masty.