Kummakivi is a large balancing rock in Ruokolahti, Finland. The 7-metre long boulder lies on a convex bedrock surface with a very small footprint but so firmly that it cannot be rocked with human force. Kummakivi ("strange stone") has been protected since 1962. A pine tree originating from the 1980s grows on top of the boulder. The boulder is located in a forest in the western part of the Ruokolahti municipality, near the border of Puumala.