Pertunmaa (Finnish: [ˈpertumˌmɑː]) is a former municipality of Finland located in the Southern Savonia region. The municipality was merged to the municipality of Mäntyharju on 1 January 2025.
The municipality had a population of 1,541 and covered an area of 454.20 km2 (175.37 sq mi) of which 79.7 km2 (30.8 sq mi) was water. The population density was 4.12/km2 (10.7/sq mi). The language of the municipality was Finnish.
Neighbour municipalities were Hartola, Heinola, Hirvensalmi, Mäntyharju and Joutsa. Pertunmaa became an independent municipality in 1926 when it was separated from Mäntyharju. Hartola's old wooden church was moved to Pertunmaa and it was inaugurated in 1927.
Due to the long-lasting economic difficulties, Pertunmaa was incorporated into Mäntyharju on January 1, 2025.
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