Kärnan (Swedish pronunciation: [ˈɕæ̂ːɳan], literally The Core) is a medieval tower in Helsingborg, Scania, in southern Sweden.

It was considered the most important fortress in Denmark, and was integral in securing control over the strait between Scania and Zealand.

The fortress was retaken by Danish forces in 1676 during the Scanian War, and its capture celebrated by flying a giant Flag of Denmark above it.

Charles XI of Sweden ordered most of it demolished fearing that it was too exposed to a sneak attack from Denmark.

[2] The castle was restored starting during 1893–94, under instructions from Oscar Ferdinand Trapp, a Swedish businessman and engineer (1847–1916).