Kozelsky District (Russian: Козе́льский райо́н) is an administrative and municipal district (raion), one of the twenty-four in Kaluga Oblast, Russia. It is located in the southeast of the oblast. The area of the district is 1,523 square kilometers (588 sq mi). Its administrative center is the town of Kozelsk. Population: 38,596 (2021 Census); 41,802 (2010 Russian census); 44,775 (2002 Census); 47,822 (1989 Soviet census). The population of Kozelsk accounts for 43.4% of the district's total population.