Gut Wahlstorf, Manor house in Wahlstorf, Germany.

Gut Wahlstorf is the oldest estate complex in Schleswig-Holstein, lying between Preetz and Plön in the municipality of Wahlstorf. Its brick manor house stands on an island formed by the Schwentine to the west and a river-fed moat to the east, reached by a several-hundred-metre lime avenue. The farm buildings flanking the central axis date from the 18th and 19th centuries.

Wahlstorf was first documented as Walestorp in 1224; in 1469 Lüder von Rumohr sold it to Detlev von Thienen, who rebuilt the island castle as a brick double house. After over 300 years with the Thienen family, the estate passed by marriage in 1788 to the Scheel von Plessen family. Until Prussia took over in 1867, the estate also held patrimonial jurisdiction.

The estate's name was first recorded as Walestorp in 1224. From 1938 Victor von Plessen, an ornithologist and explorer of the Malay Archipelago, lived here; his ethnographic collection from Indonesia and Chinese cultural objects remain in the manor house, now held by the Plessen-Stiftung Wahlstorf founded in 1997.

The manor house and farm buildings stand on an island bordered to the west by the Schwentine and to the east by a water-filled ditch fed by the same river. Access follows a several-hundred-metre lime avenue; the old limes were felled some years ago and replanted. The garden side looks across the Schwentine toward the southern part of Lanker See.

The manor's Diele, a 9.30 by 13 metre hall at the south-east corner, has a stucco ceiling attributed to Giovanni Pietro Bellasio and a round ceiling painting about 4.5 metres across, partly lost and restored in 2010. On the garden side, two old privy pillars still stand.