Bredenbek is a municipality, located in the district of Rendsburg-Eckernförde in the German Bundesland of Schleswig-Holstein.
Bredenbek is part of the Amt ("collective municipality") Achterwehr.
The Bredenbek is a tributary of the Bünzau in the north German state of Schleswig-Holstein. The river has a length of about 4 km. It rises west of Wasbek and discharges into the Bünzau west of Bargfeld.