Karlsvärd Fortress is a former fortification on the island of Enholmen near Slite on Gotland, Sweden. In its place Enholmen Fortress was built in the mid-1800s. It was decommissioned in 1905 and was then used as a training ground for the coastal artillery. During the 1990s it was used as a naval mine control station before the island was demilitarized in 2011. Karlsvärd Fortress ruin is since 2015 managed by the National Property Board.