A water castle, sometimes water-castle, is a castle where natural or artificial water is part of its defences. (It can be entirely surrounded by water-filled moats or natural waterbodies such as island castles in a river or offshore. The term comes from European castle studies, mainly German Burgenkunde. When stately homes were built in such a location, or a Wasserburg was later rebuilt as a residential manor, the German term becomes Wasserschloss, lit. "water palace/manor".

Egeskov Castle is located near Kværndrup, in the south of the island of Funen, Denmark. The castle is Europe's best preserved Renaissance water castle.