Längelmäki (known as Längelmä between 1500 and 1510) is a former municipality of Finland. Längelmäki was divided in 2007 between Jämsä and Orivesi. Längelmäki is situated by the lake Längelmävesi, from which it has got also its name. The administrative center of Längelmäki was the village of Länkipohja.
Its western parts are now part of the Pirkanmaa region and the eastern part are part of the Central Finland region. The municipality had a population of 1,734 (2003) and covered an area of 496,88 km2 of which 73,33 km2 was water (2006). The population density was 3.5 inhabitants per km2.
The municipality was unilingually Finnish.
- K. Virkkala; Ville Luho; Seppo Suvanto (1949). Längelmäveden seudun historia I. Forssan kirjapaino. p. 108.
- Maanmittauslaitos Lantmäteriverket (7 February 2006). "SUOMEN PINTA-ALA KUNNITTAIN 1. 1. 2006 | FINLANDS AREAL KOMMUNVIS 1.1.2006" (PDF). Retrieved 2015-10-25.