Kalachinsk is a town (from 1952) in Russia, the administrative centre of the Kalachinsk District of the Omsk Region. It is a railway station on the Trans-Siberian Railway.

The population of Kalachinsk is around 23.4 thousand people (as of 2009).

The town stands on the left bank of River Om, the inflow of River Irtysh, 80 km away from Omsk.

It was first recorded in the census of1795 as Kalachiki Village (with 14 homesteads and 130 dwellers), founded near Lake Kalachiki. From 1944 it was the industrial community Kalachinsk, and got the status of a town in 1952.