The Kellersee (German pronunciationⓘ) is a lake in the Holstein Switzerland region of North Germany.

At some points on the lake there are dangerous katabatic winds (Fallwinde) that are often underestimated and may lead to serious problems.

The adjacent Mondschein or Stille Bay freezes later than the lake, as does the area around the mouth of the Schwentine.

The Schwarten Fishery offers daily, weekly and monthly fishing permits for anglers.

The lake has numerous bays and striking headlands that continue underwater and form great structures for predators.