Kostomuksha is a town located in the northwestern region of the Republic of Karelia, Russia. It is situated on the shore of Lake Kontoki and lies approximately 30 kilometers (19 miles) from the border with Finland.
According to census data, the population of the town was recorded at 29,746 in 2002, which was a slight decrease from the 30,432 residents reported during the 1989 Soviet census.