The Battle of Eylau or Battle of Preussisch-Eylau, 7 and 8 February 1807, was a bloody and strategically inconclusive battle between Napoleon's Grande Armée and the Imperial Russian Army under the command of Levin August von Bennigsen near the town of Preussisch Eylau in East Prussia. Late in the battle, the Russians received timely reinforcements from a Prussian division of von L'Estocq. After 1945 the town was renamed Bagrationovsk as a part of Kaliningrad Oblast, Russia. The engagement was fought during the War of the Fourth Coalition, part of the Napoleonic Wars.
Napoleon's armies previously smashed the army of the Austrian Empire in the Ulm Campaign and the combined Austrian and Russian armies at the Battle of Austerlitz on 2 December 1805. On 14 October 1806 Napoleon crushed the armies of the Kingdom of Prussia at the Battle of Jena–Auerstedt and hunted down the scattered Prussians at Prenzlau, Lübeck, Erfurt, Pasewalk, Stettin, Magdeburg and Hamelin.
In late January Bennigsen's Russian army went on the offensive in East Prussia, pushing far to the west. Napoleon reacted by mounting a counteroffensive to the north, hoping to prevent their retreat to the east.