The Cudgel War (also Club War, Finnish: Nuijasota, Swedish: Klubbekriget) was a 1596–1597 peasant uprising in Finland, which was then part of the Kingdom of Sweden. The name of the uprising derives from the fact that the peasants armed themselves with various blunt weapons, such as cudgels, flails and maces, since they were seen as the most efficient weapons against their heavily-armoured enemies. The yeomen also had swords, some firearms and two cannons at their disposal. Their opponents, the troops of Clas Eriksson Fleming, were professional, heavily-armed and armoured men-at-arms.

Modern Finnish historiography sees the uprising in the context of the conflict between Duke Charles and Sigismund, King of Sweden and Poland (War against Sigismund). Charles agitated the peasants to revolt against the nobility of Finland, which supported Sigismund during the conflict.