Baltic Sea, a large inland sea of northern Europe. Its area is about 163,000 square miles (422,000 km2); length, slightly more than 1,000 miles (1,600 km); maximum width, about 200 miles (320 km). The Baltic is relatively shallow, rarely exceeding 350 feet (100 m) in depth. Its maximum depth is 1,539 feet (469 m). Countries bordering the sea are Sweden, Finland, Estonia, Latvia, Lithuania, Russia, Poland, Germany, and Denmark.
Major extensions of the Baltic are the Gulf of Bothnia to the north and the Gulf of Finland and Gulf of Riga to the east. The Baltic is connected to the North Sea by the Kattegat, Skagerrak, and several smaller Danish straits, and by the Kiel Canal in Germany. Canals also link the Baltic with the White Sea and with the Volga and several other rivers.
Much of the Baltic, especially along Sweden, Finland, and Estonia, has a rocky, irregular coast with numerous indentations and islands. The southern Baltic has a relatively featureless, flat or gently rolling coastline.
The water of the Baltic has a very low salt content—only about one-fifth that of the oceans. This is due to the narrow, shallow straits that restrict the inflow of salty water from the North Sea, and to the numerous rivers that drain into the Baltic. These rivers include the Oder, Vistula, Western Dvina, Neva, Torne, Ume, Angerman, and Dal. The low salinity and shallowness of the water allow ice to form along the coast in whiter, closing many Baltic ports for several months a year.
Commercial shipping and fishing are the chief economic activities in the Baltic. Polluted water is becoming an increasingly serious problem.