List of rivers of Denmark From Wikipedia, the free encyclopedia Skjern Å, the largest river in Denmark by water volume Denmark has approximately 900 streams with outlet to the sea. Almost half are less than 5 kilometres (3.1 mi) long. 52 of them are over 25 kilometres (16 mi) long and 17 are over 50 kilometres (31 mi) long.[1] The longest river is Gudenå with 156.3 kilometres (97.1 mi) while Skj..