Burg Gebhardshagen, Medieval water castle in Salzgitter, Germany.

Burg Gebhardshagen stands as a medieval water castle complex featuring an irregular arrangement of buildings around a rectangular courtyard, with remnants of the original four-winged enclosed structure and a massive northeastern corner building representing the castle's medieval core.

The castle was first mentioned in 1186 as "Burg Hagen" together with its owner Ludolf von Hagen, making it one of the oldest water castles in the Braunschweiger Land. It was destroyed in 1406 and during the Thirty Years' War and rebuilt each time. In the 16th century it became a ducal court and administrative seat, and from the mid-17th century until 1986 it served as an agricultural domain.

The castle's strategic position along the historic trade and military road connecting the episcopal seats of Minden and Halberstadt made it a crucial administrative center and fortress, reflecting medieval defensive architecture and regional feudal power structures.

The complex lies at the eastern foot of the wooded Salzgitter ridge, on the old Minden–Halberstadt road. The former Amtsteich pond beside the castle, fed by the Mühlenbach, still exists and can be seen from outside. The roughly 80 m long north wing with gatehouse, barn and Palas is the best-preserved part; the interior silos make it look like a mill.

The name Gebhard was added in 1372, when the lords of Bortfeld held the castle: Gebhard, the family's ancestral name, was joined to Hagen, giving Gebhardshagen. Earlier spellings included Gheverdeshaghen, Gebershagen and Gefershag. The surrounding settlement was called Hagen until the 16th century, when it took the castle's name.