Pääjärvi (Karstula)
Pääjärvi is a medium-sized lake of Finland. It belongs to the Kymijoki main catchment area. It is located in Karstula in the region of Keski-Suomi. Some islands are Kirkkosaari, Vuohisaari, Unikonsaari, Niittysaari and Männikkösaari.
The north part of the lake belongs to the Natura 2000 environment protection program.