Kermajärvi (literally Finn. kerma for cream, järvi for lake) is a medium-sized lake in the Vuoksi main catchment area. It is located in the region of Southern Savonia in Heinävesi. It is the country's 53rd largest lake with an area of 85.57 square kilometres (33.04 sq mi) and consists of a wide open lake with plenty of islands in both northwest and southeast parts of it and several long, narrow bays in both ends. Heinävesi parish village is located on the southern shore of the lake. A big part of the lake is protected in Natura 2000 conservation program (code FI0500011).