The Fehmarn Belt fixed link 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 Fehmarn Belt in the Baltic Sea.

There are a number of proposed fixed connections, historic and contemporary—road or rail, bridge or tunnel—designed to connect the islands of Ireland and Great Britain, connect the island of Great Britain to mainland Europe, as well as to build other connections amongst the smaller islands in the British Islands.