Bagrationovsk is a town and the administrative center of Bagrationovsky District in Kaliningrad Oblast, Russia, located close to the border with Poland, 37 kilometers (23 mi) south of Kaliningrad, the administrative center of the oblast. It has a population of 6,400 (2010 Russian census).

The Battle of Eylau, or Battle of Preussisch-Eylau, was a bloody and strategically inconclusive battle on 7 and 8 February 1807 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 part of Kaliningrad Oblast, Russia. The engagement was fought during the War of the Fourth Coalition, part of the Napoleonic Wars.