Kasteel Het Oude Loo (Castle Het Oude Loo) is dating back to the early 15th century when it was a farm, which later was fortified. When it came into the possession of the Bentinck family the moated castle as we see it today was built and enlarged between 1538 and 1540. In those days it was used as a hunting lodge by Karel, Duke of Gelre.

In 1684 Prince Willem III van Oranje, Stadtholder of Holland and Zeeland acquired the castle. He also used it as a hunting lodge. Soon the castle became too small for his hunting parties and he built Paleis Het Loo in 1686-88.

In 1795, when the French occupied Holland, the castle was used as a military hospital and it fell into neglect. In 1806 Napoleon Bonaparte appointed his brother Louis Napoleon as King of The Netherlands. Louis resided in the castle during summers. He filled up the moat around the castle.
In 1904 Queen Wilhelmina of the Netherlands ordered the restoration of the castle. This was done by the famous Dutch architect Cuypers. In the 1950's and 1960's other restoration works were carried out. Since 1968 the castle has been owned by the Dutch state. In 1973 it became a national heritage site.

Kasteel Het Oude Loo is nowadays used by the Dutch royal family as country house and guest residence. The castle itself is not open for the public, but the surrounding fenced garden/park can be visited during April and May.