Düsselburg, Medieval castle ruins in Lower Saxony, Germany.

Düsselburg is an early medieval ring rampart near Rehburg in Lower Saxony, of which an earthen wall survives. The wall forms an oval of 150 × 120 m, about 1 m high and up to 10 m wide, with a 5 m wide and 1.5 m deep pointed ditch in front. The interior is used as pasture and the wall is covered with trees.

The site began as a fortified structure in the early medieval period and underwent multiple rebuildings to meet changing needs. By the late medieval era, it declined in importance and was eventually abandoned.

The site's name reflects its historical origins as a settlement tied to water and defense. What remains visible today shows how residential spaces and fortifications existed side by side, revealing daily life during the medieval period.

The site is accessible on foot, with paths running across meadows and between the ruins. Proper footwear is recommended as the ground can become slippery in wet conditions.

The rampart is an earthwork, not masonry: a 150 × 120 m oval about 1 m high and up to 10 m wide, fronted by a 5 m wide, 1.5 m deep pointed ditch and an outer palisade wall. Excavation of the south entrance found a gate chamber 7 m square, with a burnt layer showing it burned and was rebuilt.