Lieksa is a town and municipality of Finland. It is located in the North Karelia region. The municipality has a population of 9,846 and covers an area of 4,067.60 square kilometres (1,570.51 sq mi) of which 649.14 km2 (250.63 sq mi) is water. The population density is 2.88 inhabitants per square kilometre (7.5/sq mi).