The Second Battle of Svensksund was a naval battle fought in the Gulf of Finland outside the present day city of Kotka on 9 and 10 July 1790. The Swedish naval forces dealt the Russian fleet a devastating defeat that brought an end to the Russo-Swedish War (1788–1790). The battle is the biggest Swedish naval victory and the largest naval battle ever in the Baltic Sea. It qualifies among the largest naval battles in history in terms of the number of vessels involved.

The Russo-Swedish War of 1788–1790 was fought between Sweden and Russia from June 1788 to August 1790. The war was ended by the Treaty of Värälä on 14 August 1790 and took place concomitantly with both the Austro-Turkish War (1788–1791), Russo-Turkish War (1787–1792) and Theatre War. The war was, overall, mostly insignificant for the parties involved.