Dannauer See und Hohensasel und Umgebung, protected area in the European Union defined by the habitats directive in Schleswig-Holstein, Germany

The Dannauer See und Hohensasel und Umgebung protected area covers 341 hectares, mostly a military training ground used by the Naval NCO School Plön, with 254 hectares and 97.5% inside the site. The Dannauer See, a 12.86-hectare lake, lies in the north with swamp forest and grassland shores; the Fuchsberg in Hohensasel rises to 54 meters. The area drains north via the Kossau to the Baltic Sea.

The area's conservation history began in June 2004, when the LLUR of Schleswig-Holstein drew up the NATURA 2000 standard data form; the site was proposed as a Site of Community Importance in September 2004, confirmed by the EU in November 2007 and nationally designated in January 2010. The management plan followed in June 2010, and the data form was last updated in May 2017. Because the training ground belongs to the Bundeswehr while the state administers FFH sites, a federal-state agreement reconciled military use with conservation aims.

The Dannauer See lies within the Naturschutzgebiet Dannauer See und Umgebung, which is itself fully inside the FFH area. Around the lake run several cycling and walking routes, and six information boards of the state visitor information system BIS are set up along them, with sturdy dispensers holding the leaflet published by the LLUR in September 2009. The BUND Schleswig-Holstein branch was entrusted with looking after the nature reserve.

The 254-hectare Hohensasel training ground used by the Plön naval NCO school is closed to the public; 97.5% of it lies inside the protected area. Visitors stay on the cycle and hiking paths that circle the Dannauer See, where six information boards of the state visitor system stand and hold leaflets. The lake shore is marshy in places, so waterproof footwear helps.

The military section holds the Großsteingrab Hohensasel, a Neolithic megalithic tomb, yet the training ground is closed to the public. The site also shelters the red-bellied toad (Bombina bombina), the marsh harrier and the great crested newt, all listed as conservation targets in the 2017 standard data form.