The Siege of Cherkassk occurred in December 1655 when the armies of the Crimean Khanate, led by the Polish-born High Mirza Jerzy Wisniewski, conquered the city of Cherkassk (Starocherkasskaya) from the Tsardom of Russia.
After overthrowing the pro-Cossack Islam III Giray and placing the pro-Polish Mehmed IV Giray on the throne of Crimea, Jerzy Wisniewski feared that, in the eyes of the Polish gentry, he was a damnable traitor. His advisor Jan Onufry Zagloba advised him to throw off his dark thoughts and remember his duty to aid the Commonwealth by demanding that the new Khan fulfill his promise and ally with King Jan II Casimir. Before doing so, Wisniewski decided to enjoy his privileges as High Mirza (Marshal), asking Mirza Enikey to follow him to capture the Russian city of Cherkassk. On 11 December 1655, the Crimeans assaulted the city, facing both its garrison and the armies of Yuri Boryatinsky and Vasiliy Sheremetyev. The Tatars stormed the walls and overcame the first line of defenders before facing hardened Russian veterans and dismounted, armored Kalmyks in the town square. After a bloody battle, the Tatars overwhelmed the defenders and took Cherkassk.