The Battle of Grengam, a naval battle that took place on July 27 (August 7) 1720 in the Baltic Sea near Grengam Island, was the last significant clash of the Great Northern War.

Despite numerous defeats on land and at sea, Sweden continued to avoid signing a peace treaty with Russia, as this would mean legally recognizing the loss of its status as a leading power in Northern and Eastern Europe. At the same time, such a treaty would solidify Russia's role as the main force in the region. The Russian-Swedish Åland Congress, held from May 1718 to September 1719, did not lead to peace. Meanwhile, the growing Russian fleet began to threaten Britain's influence in the Baltic Sea.

The squadron commanded by M. M. Golitsyn achieved significant success when on July 27 (August 7) 1720, it lured Swedish forces, including 1 ship of the line, 4 frigates, 1 galley, and several smaller vessels, into the Grengam Bay, filled with underwater rocks and shallows. In such conditions, the Swedish ships lost their ability to maneuver.

When the Russian ships approached Grengam, the Swedish fleet under K.-G. Schöblad, armed with 156 guns, unexpectedly weighed anchor and moved in for engagement, subjecting the Russians to intense fire. The Russian fleet began to retreat quickly into shallow waters, where the pursuing Swedish ships also ended up. In the shallows, the more maneuverable Russian galleys and boats launched an attack and managed to board 4 frigates (the 34-gun 'Stor-Phoenix', the 30-gun 'Venker', the 22-gun 'Kiskin', and the 18-gun 'Dansk-Ern'), after which the remaining part of the Swedish fleet retreated.

The Battle of Grengam marked the end of Sweden's unchallenged influence in the Baltic Sea and established Russia's presence there. The battle brought the conclusion of the Treaty of Nystad closer.

In September 1720, celebrations were held in St. Petersburg in honor of the victory at the Battle of Grengam.