Glücksburg Castle (German: Schloss Glücksburg, Danish: Lyksborg Slot) is a water castle (Wasserschloss) in the town of Glücksburg, Germany. It is one of the most important Renaissance castles in northern Europe. It is the seat of the House of Schleswig-Holstein-Sonderburg-Glücksburg and was also used by the Danish kings. Situated on the Flensburg Fjord the castle is now a museum owned by a foundation, and is no longer inhabited by the ducal family.