The Battle of Svensksund was fought during the 1788–1790 war between Russia and Sweden.

Swedish king Gustav III started the war. He and the Russian tsaress Catherine the Great were cousins. The war culminated in the second battle of Ruotsinsalmi (Svensksund in Swedish, approximately "Swedish Strait" in English) on 9–10 July 1790.

The battle of Ruotsinsalmi was the biggest naval battle ever at the time: 500 ships, 30,000 men and 3,000 cannons. Even today, only the Battle of Leyte Gulf has been larger. In Ruotsinsalmi, the Swedes destroyed 40 percent of the Russian coastal fleet.

The war ended on August 14, 1790, and neither party gained any territory.