The Battle of Königgrätz was the decisive battle of the Austro-Prussian War in which the Kingdom of Prussia defeated the Austrian Empire. It took place on 3 July 1866, near the Bohemian city of Hradec Králové and village of Sadová, now in the Czech Republic. It was the single largest battle of the war, and the largest battle in the world since the Battle of Leipzig in 1813.

The Austro-Prussian War, also by many variant names such as Seven Weeks' War, German Civil War, Brothers War or Fraternal War, known in Germany as Deutscher Krieg, Deutscher Bruderkrieg and by a variety of other names, was fought in 1866 between the Austrian Empire and the Kingdom of Prussia, with each also being aided by various allies within the German Confederation. Prussia had also allied with the Kingdom of Italy, linking this conflict to the Third Independence War of Italian unification. The Austro-Prussian War was part of the wider rivalry between Austria and Prussia, and resulted in Prussian dominance over the German states.