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. Trying to realize promises given by Jogaila during the war, Teutonic Order organized the negotiations for the treaty.[1] The acts were signed after six days of negotiations on an island in the mouth of the Dubysa River.[2] The treaty was never ratified and never came into effect. The civil war resumed in summer 1383.