Gut Altenhof, Cultural heritage manor house in Altenhof, Germany.

Gut Altenhof is a manor estate in the municipality of Altenhof in Schleswig-Holstein. Its main house, built 1722–1728 for Cay Friedrich von Reventlow, was remodeled in Neoclassical style in the 19th century, then Neo-Gothic in 1863, and given Neo-Baroque side wings by architect Paul Schultze-Naumburg in 1904–1910. The estate includes a park with the remains of a medieval motte and is still owned by the von Bethmann Hollweg family.

Cay Friedrich von Reventlow built the core of the present manor house between 1722 and 1728, after erecting the large estate buildings. The house was remodelled in Neoclassical style in the 19th century and given a Neo-Gothic appearance in 1863. From 1904 to 1910 Paul Schultze-Naumburg replaced old annexes with new side wings and gave the whole building a Neo-Baroque form. After World War II it housed the British Regional Commissioner (from 1946) and Land Commissioner (from 1949) of Schleswig-Holstein.

The estate hosts musical performances during the Schleswig-Holstein Music Festival, bringing concerts to its historic spaces and grounds. These events create a connection between the property's past and present cultural use.

The grounds are accessible during the golf season, with facilities available for players and visitors on site. The historic rooms can sometimes be explored during special events, so checking the event calendar beforehand is helpful.

Within the park lies the remains of a medieval motte, an early earthen fortification that predates the current mansion. This archaeological layer reveals how the site was inhabited in different historical periods.