Vainius

Vainius, also called Voin, was the Lithuanian prince of Polotsk and a brother of Grand Duke Gediminas, held to be a son of Butvydas. First recorded in 1324, he already ruled Polotsk, and in 1326 joined Gediminas' embassy to Novgorod to make peace with the Novgorodians and the Livonian Order.

He probably died during the Order's campaigns against Polotsk in 1333–1334, and by 1338 Narimantas held the city. His only known son Liubartas was killed fighting the Order in 1342.