Jämsä is a town and municipality of Finland. It is located in the Central Finland region, about 58 kilometres (36 mi) southwest of Jyväskylä. The municipality has a population of 19,182, which makes it the second largest town of the Central Finland after Jyväskylä. It covers an area of 1,823.90 square kilometres (704.21 sq mi) of which 252.57 km2 (97.52 sq mi) is water. The population density is 12.21 inhabitants per square kilometre (31.6/sq mi).

Central Finland is a region in Finland. It borders the regions of Päijät-Häme, Pirkanmaa, South Ostrobothnia, Central Ostrobothnia, North Ostrobothnia, North Savo, and South Savo. The city of Jyväskylä is the regional centre and by far the largest city in the area. The Central Finland lies slightly south of the geographical centre of Finland. The landscape is hilly and a large part of the province belongs to the Finnish Lakeland.