Puruvesi is a lake in Eastern Finland. The lake is located in Kerimäki, Kesälahti and Punkaharju municipalities. Part of the Saimaa lake system, it borders on the sub-lake system of Pihlajavesi to the south. As is the case of other lakes of Saimaa, it has numerous islands and consists of numerous open lake areas, of which largest are Hummonselkä, Pajuselkä, Sammalselkä, Mustanselkä, and Ruosteselkä.