Kärnan (Swedish pronunciation: [ˈɕæːˈɳan]; Danish: Kernen, both literally The Core) is a medieval tower in Helsingborg, Scania, in southern Sweden. It is the only part remaining of a larger Danish fortress which, along with the fortress Kronborg on the opposite of Oresund, controlled the entranceway between Kattegat and Øresund and further south the Baltic Sea.