Kozelsk (Russian: Козе́льск) is a town and the administrative center of Kozelsky District of Kaluga Oblast, Russia, located on the Zhizdra River (Oka's tributary), 72 kilometers (45 mi) southwest of Kaluga. Population: 18,245 (2010 Census); 19,907 (2002 Census); 19,735 (1989 Census).