Vaišvilas was a Lithuanian noble and sometimes is considered as one of the sons of Kęstutis

Kestutis

Kęstutis was monarch of medieval Lithuania. He was the Duke of Trakai and governed the Grand Duchy of Lithuania, 1342–82, together with his brother Algirdas , and with his nephew Jogaila...

, Grand Duke of Lithuania. In 1358 Kęstutis and Masovian princes formed a commission to settle border disputes. The Lithuanian side was represented by Vaišvilas (Woyszwylt), Patirgas, possibly another son of Kęstutis, and Eikšis, son of Karijotas. This leads historians to believe that Vaišvilas ruled some area bordering Masovia. In 1367 a treaty with Livonia

Livonia

Livonia is a historic region along the eastern shores of the Baltic Sea. It was once the land of the Finnic Livonians inhabiting the principal ancient Livonian County Metsepole with its center at Turaida...

 mention Vaišvilas as Waysewist. Later he is found in Lahojsk

Lahojsk

Lahojsk is a city in the Minsk Province of Belarus, an administrative center of the Lahojsk district. This city has a ski resort named Silichy.-External links:* * *...

, now Belarus

Belarus

Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...

. There are theories that an unnamed "nobilis satrapa" who died at the Battle of Rūdava in 1370 was Vaišvilas. He probably died before 1385 or 1387 because he is not mentioned during turbulent civil wars between Vytautas the Great

Vytautas the Great

Vytautas ; styled "the Great" from the 15th century onwards; c. 1350 October 27, 1430) was one of the most famous rulers of medieval Lithuania. Vytautas was the ruler of the Grand Duchy of Lithuania which chiefly encompassed the Lithuanians and Ruthenians...

 and Jogaila

Jogaila

Jogaila, later 'He is known under a number of names: ; ; . See also: Jogaila : names and titles. was Grand Duke of Lithuania , king consort of Kingdom of Poland , and sole King of Poland . He ruled in Lithuania from 1377, at first with his uncle Kęstutis...

.