Vygantas (baptized Alexander; Polish: Wigunt; died June 28, 1392 in Vilnus) was Duke of Kernav?. He was one of the sons of Algirdas, Grand Duke of Lithuania (1345-1377), and his second wife Uliana Alexandrovna of Tver.
In 1385, Vygantas supported his older brother Jogaila by signing the Union of Krewo. On February 18, 1386, he was baptized as Alexander. In the same year he was bethroted to Jadwiga, daughter of W?adys?aw Opolczyk. He married her in 1390. Polish nobles expected that W?adys?aw would grant Vygantas the Dobrzy? Land, a contested territory between Poland and the Teutonic Knights, as his dowry. Vygantas received Kuyavia from Jogaila instead. In 1388, he supported Poland in an armed conflict with the Teutonic Knights. He also supported W?adys?aw Jagieo (Jogaila) in the Lithuanian Civil War (1389-1392) against Vytautas. Vygantas was considered as a replacement for unpopular Skirgaila as Grand Duke of Lithuania. However, he soon died in Vilnus. The rumors had it that he was poisoned - either by Vytautas or Skirgaila. He is buried in Vilnius Cathedral together with his brother Karigaila, who died in the civil war in 1390.
Vygantas should not be confused with his brother Andrei of Polotsk, who is sometimes referred to as Wigunt-Andrei following the confused 15th-century chronicles of Jan D?ugosz.Kazimierz Stadnicki in his work Bracia W?adys?awa-Jagiey Olgierdowicza (published in 1867) suggested that Vygantas and his elder brother Theodore were the same person, but this theory was rejected.