The twin battles of Jena and Auerstedt (older name: Auerstädt) are fought on October 4, 1806 on the plateau west of the river Saale in today's Germany, between the forces of Napoleon I of France and Frederick William III of Prussia.

The decisive defeat suffered by the Prussian Army subjugates the Kingdom of Prussia to the French Empire until the Sixth Coalition is formed in 1812.

Several figures integral to the reformation of the Prussian Army participate at Jena–Auerstedt, including Gebhard von Blücher, Carl von Clausewitz, August Neidhardt von Gneisenau, Gerhard von Scharnhorst, and Hermann von Boyen.