Abo (Swed. Abo), a city of Russia, in Finland, capital of the government of Abo-Bjor-neborg, built on both sides of the Aurajoki, not far from where it flows into the gulf of Bothnia, 260 m. W. by X. of St. Petersburg; pop. in 1870, 21,830. It was founded in 1157 by the Swedes, and was the capital of Finland till 1819. A bishopric was established here in the 13th century. In 1827 the greater part of the city was destroyed by fire, including the university buildings and the library, containing 40,000 volumes. The university was rebuilt in Helsingfors, the new capital of the province. Abo is still the seat of considerable trade. - The peace of Abo, concluded Aug. 17, 1743, between Sweden and Russia, terminated the struggle between those countries commenced in 1741, at the instigation of France, in order to prevent Russia's participation in the war of the Austrian succession. During this contest, the blunders of the Swedish generals enabled the Russians to take poss3ssion of Finland. The empress Elizabeth offered to restore the greater part of the province, on condition that Sweden should elect Prince Adolphus Frederick of Holstein-Eutin successor to the throne.

This demand Sweden complied with July 4, 1743.