The Battle of Ratan was the last battle fought on Swedish soil during the Russian-Swedish War of 1808 - 1809. It took place a day apart from the Battle of Sävar, on 20 August 1809. Having conquered Finland from Sweden, the Russians had a small force in the northern areas of Sweden. The Swedes sought to eliminate this through a combined assault from land and sea, but the Russians moved more rapidly, defeating the Swedish force landed at Ratan at Sävar on 19 August. The next day, on 20 August, the Swedish riflemen was attacked and pushed out of Ratan, turning to the flotilla and starting the evacuation. At the same time, artillery fire from Swedish warships kept the Russians at bay. Peace negotiations followed the heavy fighting.

The Finnish War was fought between the Kingdom of Sweden and the Russian Empire from 21 February 1808 to 17 September 1809 as part of the Napoleonic Wars. As a result of the war, the eastern third of Sweden was established as the autonomous Grand Duchy of Finland, a state under the rule of the Russian Empire. Other notable effects were the Swedish parliament's adoption of a new constitution and the establishment of the House of Bernadotte, the new Swedish royal house, in 1818.