Treaty of Abo

The Treaty of Abo concluded the Russo-Swedish War of 1741 to 1743, sometimes called the Hats' War, which Sweden had launched in hopes of recovering territory lost to Russia under Peter the Great. The campaign went badly for Sweden, whose forces were defeated and pushed back, leaving Russian armies in control of much of Finland and Sweden in a weak negotiating position.

Signed in 1743 at Abo, the Finnish town now known as Turku, the treaty restored peace between Russia and Sweden. Sweden was compelled to cede a strip of southeastern Finland, including the area around Kymmene, to Russia, advancing the frontier westward. In return, Russia returned most of the occupied Finnish territory it had overrun during the war.

As a further condition, the Swedish parliament agreed to elect the Russian-favored candidate, Adolf Frederick of Holstein-Gottorp, as heir to the Swedish throne. This concession reflected Russia's growing dominance over Baltic affairs and Swedish politics in the eighteenth century. The treaty confirmed Sweden's decline as a great power and the steady expansion of Russian influence along the Baltic.