The names Vänersborg means "fortress at Vänern". It comes from the fortlet which was begun on in 1644 for protection.
Around 1800, Vänersborg had a population of 1,500 inhabitants. After the inauguration of the canal at Trollhättan and the Göta älv, creating a waterway between Vänern and Gothenburg, its importance further grew.
In 1834, most of the city with its wooden houses burnt down. Thereafter it was rebuilt according to a check pattern.
The poet Birger Sjöberg (1885-1929) was born in Vänersborg. He wrote appreciative about Vänersborg, most notably in Fridas bok (1922), wherein the comparisment "Vänersborg -- little Paris" is found. The park in the northern part of Vänersborg, Skräckleparken, offers a picturesque view over lake Vänern, and therein also stands this statue of mentioned Frida.