Kozelsk is a town and the administrative center of Kozelsky District in Kaluga Oblast, Russia, located on the Zhizdra River, 72 kilometers (45 mi) southwest of Kaluga, the administrative center of the oblast. Population: 16,759 (2021 Census); 18,245 (2010 Russian census); 19,907 (2002 Census); 19,735 (1989 Soviet census).

Kaluga Oblast is a federal subject of Russia. Its administrative center is the city of Kaluga. The 2021 Russian Census found a population of 1,069,904.