Iselingen is a manor house and estate located close to Vordingborg on the southern part of Zealand in southeastern Denmark.

Iselingen was created when the former Vordingborg Cavalry District was divided into 12 estates and sold in auction by the crown in 1774.

The castle was a ruin but the land and its tenant farms were acquired by the merchant Reinhard Iselin who gave it the name Iselingen.

Datteren Marie Margrethe was married to Christian Frederik Ernst Rantzau but the couple was—highly unusually for the time—divorced in 1793.

In 1802, she began the construction of a new main building at a site located to the northeast of the old castle ruin.

Recently engaged to 18-year old Marie Koës, he consulted his fiancé on the matter and she responded with a "Yes let's move to Iselingen, then I can have a large garden with lots of flowers and strawberries!".

His visitors at Iselingen included the Ørsted brothers, Grundtvig, Bertel Thorvaldsen, Adam Oehlenschläger and Christian Winther.

Iselingen was therefore passed on to Holger Aagaard's son-in-law Martin Hammerich, a scholar specializing in Norse linguistics, culture, history.

After the death of her husband Ove Morton Middelboe Bille Hansen (1877-1957) in 1957, she ceded it to their daughter Tove, Countess of Ahlefeldt–Laurvig.