The Treaty of Dubysa or Treaty of Dubissa (Lithuanian: Dubysos sutartys) consisted of three legal acts formulated on 31 October 1382 between Jogaila, Grand Duke of Lithuania, with his brother Skirgaila and Konrad von Wallenrode, Marshal of the Teutonic Order.
During the Lithuanian Civil War (1381–84), Teutonic Order helped Jogaila and Skirgaila to defeat their uncle Kęstutis and his son Vytautas.
In the first act Jogaila promised to baptize himself and convert the Grand Duchy of Lithuania to Christianity within four years.
[1] All three acts (only two originals survive, the third is known from a transcript made in 1410)[1] were signed by all sons of Algirdas and Uliana of Tver (Jogaila, Skirgaila, Kaributas, Lengvenis, Karigaila, Vygantas, and Švitrigaila) and by Hanul,[2] a merchant from Vilnius who opened the city gates in June 1382, allowing Jogaila to depose Kęstutis.
[1] Kęstutis died in a prison cell of the Kreva Castle on 15 August 1382 while Vytautas managed to escape a few months later and asked the Order for help and protection.
Jogaila arrived as agreed, but the Teutonic delegation, led by Grand Master Conrad Zöllner von Rothenstein, got stuck near Skirsnemunė, just a few miles away from their destination, due to shallow water in the Neman River.