Yury Svyatoslavich or Georgy Svyatoslavovich (Russian: Юрий Святославович or Георгий Святославович) was the last sovereign ruler of the Principality of Smolensk and Bryansk (1386–95, 1401–04) whose life was spent in vain attempts to fend off aggression by the Grand Duchy of Lithuania.
In 1386 a war broke out between Algirdas' sons, Skirgaila and Andrei of Polotsk. The latter fled from Polotsk to Smolensk and asked Yury's father for help. The armies of Smolensk and Skirgaila clashed near Mstislavl in the Battle of the Vikhra River. After Yury's father was killed in battle and his brothers were taken prisoner, the Lithuanians approached Smolensk and allowed Yury to assume the throne on certain conditions, after exacting a sizable indemnity from him.
In 1395, while Yury was visiting his father-in-law, Oleg Korotopol of Ryazan, Grand Duke Vytautas the Great (Vitovt) of Lithuania took Smolensk and installed his governor there. Four years later, Vytautas was routed by the Tatars in the Battle of the Vorskla River. In 1401, Yury and Oleg made use of his plight to retake Smolensk and Bryansk, where the pro-Lithuanian boyars were promptly executed.
In fall 1401, Vytautas laid siege to Smolensk but was forced to retreat after signing an armistice. Two years later, Smolensk withstood a two-week siege by Vytautas. Solicitous to preclude a new attack, Yury went to the Grand Duchy of Moscow to ask Vasily I for help against Vytautas (who was Vasily's father-in-law). Although Yury promised to bequeath his possessions to Vasily, the Muscovite ruler hesitated to accept this proposal, until the boyars of Smolensk opened the city gates to Vytautas and surrendered Yury's capital to his old enemy in 1404. Thus Smolensk was lost to Russians for more than a century.