Kozelsk (Russian: Козе́льск) is a town and the administrative center of Kozelsky District in Kaluga Oblast, Russia, located on the Zhizdra River (a tributary of the Oka), 72 kilometers (45 mi) southwest of Kaluga, the administrative center of the oblast.

Kozelsk became famous in the spring of 1238, when its twelve-year-old prince Vasily, son of Titus, had to defend the town against the army of Batu Khan.

The latter dubbed it an "evil town" because its citizens had been fighting the attackers for seven weeks in a row, killing around four thousand enemy soldiers during the siege.

In 1607, one of Ivan Bolotnikov's units was located in Kozelsk and showed resistance to the Tsar's army.

[3] After World War II, Kozelsky District became the home for the 28th Guards Rocket Division of the Strategic Missile Troops.