The River Guden (Danish: Gudenåen, pronounced [ˈɡuˀðn̩ˌɔːˀn̩]), on the Jutland peninsula, is Denmark's longest river. It flows 176 kilometres from Tinnet Krat in Vejle County, between Nørre Snede and Tørring-Uldum, to Randers Fjord in Randers, on a course which takes it through central Jutland. On its way it traverses the lakeland waters of Sminge Sø (Lake Sminge), Silkeborg Langsø, Brassø, Borre Sø, Julsø, Biksø, Rye Mølle Sø, Gudensø, Mossø, Vestbirk Sø, and Naldal Sø.
The Guden came into existence some 15,000 years ago during the last Ice Age, when ice and glacial streams carved out its bed. It shelters many species of animal.