The Russo-Swedish siege of Vilna occurred in 1655 when a combined Russian-Swedish army under Prince Ivan Sontsov-Zasekin and Ratsherr Fabian von Wersen besieged the Polish-Lithuanian city of Vilna (Vilnius, Lithuania). The allied army was defeated by the Poles in a battle fought before the city walls.
During King Charles X Gustav of Sweden's invasion of Poland-Lithuania, Swedish armies descended from Livonia and Brandenburg to attack northern Poland as the Russians invaded the Smolensk Voivodeship and the Cossack Hetmanate conquered right-bank Ukraine from the Poles. In May 1655, a combined Russo-Swedish army laid siege to Vilna, the capital of the Grand Duchy of Lithuania, and several prominent Polish nobles and their armies hastened to the city's defense. The superiority of the Poles' cavalry was established in the ensuing series of battles as Polish horsemen easily rode down the Russian and Swedish musketeers and encircled their pikemen. When the Russians sent in their cavalry to carry out the final attack on the Polish army, they were bogged down while crossing a river and were overwhelmed by a charge of Polish cavalry and infantry. The Poles destroyed the Russo-Swedish army and temporarily saved Vilnius, although it would fall under Swedish control later that month. The future Polish king, Hetman Jan Sobieski, was rescued from captivity during the battle, causing him to befriend the ambitious Wisniewski.