Schloss Diepholz, Heritage monument in Diepholz, Germany

Schloss Diepholz is a castle situated in the center of the town in Lower Saxony. The structure displays typical features of northern German castle architecture with thick walls and building elements spanning multiple historical periods.

A water castle was first documented in 1233, though members of the von Diepholz family appear in Osnabrück diocese charters from 1160. In 1510 the lords of Diepholz granted their rule to the Dukes of Brunswick-Lüneburg as a fief. A fire destroyed the castle around 1522 and it was rebuilt in Renaissance style; around 1550 Rudolf von Diepholz had it altered before moving in with Countess Margarete von Hoya. Danish troops burned it in the Thirty Years' War and Swedish troops destroyed it in 1637; it was repaired in 1651 and raised by one storey. A 1790 fire ruined the south wing and parts of the west wing, and since 1852 the Diepholz district court has sat in the castle.

The stone frieze above the north door, carved around 1550, shows the coats of arms of the von Diepholz and von Hoya families, recalling the marriage of Rudolf von Diepholz and Countess Margarete von Hoya. Since 1852 the castle has housed the Diepholz district court, and the tower holds the Museum im Schlossturm.

The castle stands in the town centre of Diepholz. The district court (Amtsgericht) has used the building since 1852, so the wings are not open to visitors; the museum in the 43-metre tower can be visited. The tower's lower 16.5 metres are granite blocks, above which rise a twelve-sided brick storey and a timber-framed one.

The oldest part is the 43-metre north tower, whose lower 16.5 metres are laid in granite blocks up to 3.5 metres thick, topped by a twelve-sided brick storey and a timber-framed floor from around 1660. A stone frieze above the north door shows the coats of arms of the Diepholz and Hoya families, carved after Rudolf von Diepholz rebuilt the castle around 1550.