Fehmarn Belt in the context of "Bay of Kiel"

The Danish straits are the straits connecting the Baltic Sea to the North Sea through the Kattegat and Skagerrak. Historically, the Danish straits were internal waterways of Denmark; however, following territorial losses, Øresund and Fehmarn Belt are now shared with Sweden and Germany, while the Great Belt and the Little Belt have remained Danish territorial waters. The Copenhagen Convention of 1857 made all the Danish straits open to commercial shipping. The straits have generally been regarded as an international waterway.

The Fehmarn Belt fixed link (Danish: Femern Bælt-forbindelsen, German: Fehmarnbelt-Querung) or Fehmarn Belt tunnel is an under-construction immersed tunnel, which will connect the Danish island of Lolland with the German island of Fehmarn, crossing the 18-kilometre-wide (11 mi) Fehmarn Belt in the Baltic Sea. The tunnel is intended to be a major wider connection between mainland Europe and Scandinavia.

The tunnel is planned to become world's longest road and rail (combination) tunnel and will directly replace a heavily travelled ferry service of the "Bird flight line" (German: Vogelfluglinie; Danish: Fugleflugtslinjen) operated by Scandlines. The tunnel will provide a direct link from northern Germany to Lolland, with Fehmarn connected with the German mainland by the Fehmarn Sound Bridge and Lolland connected by a tunnel and bridges with the Danish island of Zealand, which includes Copenhagen, via the island of Falster. The Fehmarn Belt project will therefore provide a more direct and efficient connection between Germany and Zealand (which in turn is connected with the Swedish mainland via the Øresund Bridge), compared to the existing road-rail link that is the detoured Great Belt Bridge via Jutland and Funen. Travel time between Lolland and Fehmarn is to be reduced from 45 minutes by ferry (excluding waiting and boarding time) to 10 minutes by car and seven minutes by train. The electrified high-speed rail line will be capable of reaching 200 km/h (125 mph).

Fehmarn (German: [ˈfeːma⁠ʁn] ; Danish: Femern; from Old Wagrian Slavic "Fe More", meaning "In the Sea") is an island in the Baltic Sea, off the eastern coast of Germany's northernmost state of Schleswig-Holstein. It is Germany's third-largest island, after Rügen and Usedom. Fehmarn is separated from the German peninsula of Wagria in Holstein by the Fehmarn Sound, and from the southern Danish island of Lolland by the Fehmarn Belt. It is connected to the Holsatian mainland by the Fehmarn Sound Bridge. The island belongs to the district of Ostholstein (East Holstein). The closest larger towns on the mainland are Heiligenhafen (Saints’ Harbor) and Oldenburg in Holstein (founded as Starigard). Right opposite Fehmarn, on the tip of the Wagrian Peninsula, is Großenbrode.

The Vogelfluglinie (Danish: Fugleflugtslinjen), an important transport corridor connecting the Danish capital of Copenhagen on the island of Zealand to the second-largest German city of Hamburg via Lübeck, runs across the island. There are currently two tunnels under construction in the region: the Fehmarn Belt Tunnel between Puttgarden on Fehmarn and Rødbyhavn on Lolland, and the Fehmarn Sound Tunnel between Strukkamp (Fehmarn) and Großenbrode (Wagria). The most notable settlements on Fehmarn are Burg auf Fehmarn (Low German: Borg op Fehmarn) and Puttgarden, with the island's ferry port.