Kalachinsky District is an administrative and municipal district (raion), one of the thirty-two in Omsk Oblast, Russia. It is located in the southeast of the oblast. The area of the district is 2,800 square kilometers (1,100 sq mi). Its administrative center is the town of Kalachinsk. Population: 18,197 ; 21,810 (2002 census); 22,812 (1989 Soviet census).