The Battle of Tannenberg was a World War I battle fought in the area south of Allenstein in East Prussia between German and Russian armies from August 26 to August 30, 1914. The German side fielded 153,000 soldiers, the Russian 191,000. It ended with a victory for the German troops and the crushing of the Russian forces that had penetrated into southern East Prussia.

Initially referred to in the German media as the "Battle of Allenstein," it was renamed the Battle of Tannenberg for propaganda purposes shortly thereafter at the request of Paul von Hindenburg. In fact, it is not the village of Tannenberg (today Stębark) that lies directly in the main battle area, but Hohenstein.