Fehmarn Belt fixed link

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 the 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).

Designed and financed by Danish state-owned Femern A/S, the tunnel was approved in 2015 with a construction budget of 52.6 billion krone (equivalent to US$8.2 billion), making it the largest traffic investment in Denmark's history, which will be partly recouped by tolling the tunnel. Germany plans to pay a further €800 million to connect the crossing to its motorway network. The Fehmarnbelt tunnel is expected to be completed in 2031.