Mariinsk is a town in Kemerovo Oblast, Russia, where the Trans-Siberian Railway crosses the Kiya River, 180 kilometers (110 mi) northeast of Kemerovo, the administrative center of the oblast. Population: 40,526 (2010 census); 42,977 (2002 census); 40,956 (1989 Soviet census); 39,700 (1972).