Least salty sea
Baltic Sea
7–8 grams salt per kilogram of water total number
Not Applicable ()

The Baltic Sea in northern Europe has the lowest salinity of any sea, with an average salt concentration of 7–8 grams per kilogram of water (meaning that the water is 0.7–0.8% salt by weight). The sea's extremely low salinity is a consequence of its enclosed geography (it is almost completely cut off from the World Ocean, with just the narrow Danish Straits connecting it to the North Sea), low rate of evaporation (it is very cold), and the large number of major rivers that flow into it.

There is significant variation in salinity between different parts of the Sea – with salt concentrations of between 10 and 32.7 g/kg in the Danish Straits and as low as 1 g/kg in the Gulf of Riga and the Gulf of Bothnia.

The least saline ocean, by comparison, is the Arctic Ocean, which has a typical salinity of 28–30 g/kg owing to the low rate of evaporation and meltwater from the ice-caps.