The Kattegat (Danish, from Dutch, commonly used in English), or Kattegatt (Swedish) is a sea area bounded by the Jutland peninsula and the Straits islands of Denmark on the west and south, and the provinces of Västergötland, Scania, Halland and Bohuslän in Sweden on the east. The Baltic Sea drains into the Kattegat through the Danish Straits. The Kattegat is a continuation of the Skagerrak and may be seen as either a bay of the Baltic Sea, a bay of the North Sea, or, in traditional Scandinavian usage, neither of these.
According to the definition established in a 1932 convention signed by Denmark, Norway and Sweden (registered in the League of Nations Treaty Series 199 - 1933), the northern boundary between Kattegat and Skagerrak is found at the northernmost point of Skagen on Jutland and the southern boundary towards Øresund is found at the tip of Kullen Peninsula in Scania.
Waterways that drain into the Kattegat are the rivers of Göta älv at Gothenburg, together with the Lagan, Nissan, Ätran and Viskan from the province of Halland on the Swedish side, and the river of Gudenå from Jutland, in Denmark.
A number of noteworthy coastal areas abut the Kattegat, including the Kullaberg Nature Reserve in Scania, Sweden, which contains a number of rare species and a scenic rocky shore, the town of Mölle, which has a picturesque harbour and views into the Kullaberg, and Skagen at the northern tip of Denmark.
Currently, a proposed bridge from Jutland to Zealand across the southern part of Kattegat is under political consideration in Denmark, linking the islands of Zealand and Samsø with continental Denmark.
- On the South. The limits of the Baltic Sea in the Belts and Sound:
- In the Little Belt. A line joining Falshöft ( ) and Vejsnæs Nakke (Ærö: ).
According to Den Store Danske Encyklopædi and Nudansk Ordbog, the name derives from the Dutch words kat (cat) and gat (hole, gate). It refers to late medieval navigation jargon, when captains of the Hanseatic trading fleets would compare the Danish Straits to a hole so narrow that even a cat would have difficulty squeezing its way through on account of the many reefs and shallow waters. At one point, the passable waters were a mere 3.84 kilometers (2.39 mi) wide. The name of the Copenhagen street Kattesundet has the same etymological meaning, namely "narrow passage".
This was one of the first marine dead zones to be noted in the 1970s, when scientists began studying how intensive economic use affected the natural world.
See also 
- Convention No 3210. League of Nations Treaty Series 139, 1933. Retrieved 27 December 2012.
- "Limits of Oceans and Seas, 3rd edition". International Hydrographic Organization. 1953. Retrieved 6 February 2010.
- Den Store Danske Encyklopædi (2004), CD-ROM edition, Copenhagen: Gyldendal, entry Kattegat.
- Nudansk Ordbog (1993), 15th edition, 2nd reprint, Copenhagen: Politikens Forlag, entry Kattegat.
- "Cattegat, The". New International Encyclopedia. 1905.