Vänern is the largest lake in Sweden, the largest lake in the European Union and the third-largest lake in Europe after Ladoga and Onega in Russia. It is located in the provinces of Västergötland, Dalsland, and Värmland in the southwest of the country. With its surface located at 44 metres (144 ft) with a maximum depth of 106 metres (348 ft), the lowest point of the Vänern basin is at 62 metres (203 ft) below sea level. The average depth is at a more modest 28 metres (92 ft), which means that the average point of the lake floor remains above sea level.

Västergötland, also known as West Gothland or the Latinized version Westrogothia in older literature, is one of the 25 traditional non-administrative provinces of Sweden, situated in the southwest of Sweden.