The Sound, Danish Øresund, Swedish Öresund , strait between Zealand (Sjælland), Denmark, and Skåne, Sweden, connecting the Kattegat strait (northwest) with the Baltic Sea (south). The Sound is one of the busiest sea lanes in the world.
Its total length, between the Kullen peninsula in the north and Falsterbo in the south (both in Sweden), is 70 miles (110 km). The more landlocked portion, between Helsingør-Helsingborg in the north (width 3 miles [5 km]) and Copenhagen-Malmö in the south (width 9 miles [14 km]), is 33 miles (53 km) long. The strait has a minimum depth of 23 feet (7 metres) and a surface current flowing up to 3 to 4 miles (5 to 6 km) per hour toward the Kattegat. Ice in the almost tideless strait may impede navigation in severe winters. Three large islands lie in The Sound: Amager (partly embraced by Copenhagen), Ven, and Saltholme. These divide the waters into the channels of Drögden (west) and Flinterenden (east).
The principal ports are Copenhagen and Helsingør (Elsinore) on the Danish side and Malmö and Helsingborg on the Swedish side. In 2000 the Øresund Link, a bridge and tunnel system connecting Malmö and Copenhagen, opened and was expected to spur economic growth and cooperation in the region. The Sound has long been an important commercial sea lane. In the past, political control of The Sound, the shortest route from the Kattegat to the Baltic, conferred great commercial benefits. Between 1429 and 1657, Denmark controlled both shores and exacted tolls from all shipping passing through. Even after Skåne was annexed by Sweden in 1658, the great Danish coastal fortress of Kronborg at Helsingør continued to levy The Sound toll until 1857.