Haus Niedernhofen, Former knight's estate in Hagen-Hengstey, Germany.

Haus Niedernhofen is an architectural structure in Hagen-Nord that developed on an estate along the Ruhr River. The grounds sit near the modern Hengsteysee, a dammed section of the waterway that shaped the landscape's current appearance.

The estate belonged to the Ovelacker family from the medieval period and served as their regional seat of power. Their control of the property lasted until the 18th century, after which the land changed hands and took on different purposes.

The name recalls the Ovelacker family, who held Niedernhofen as a fief from the lords of Volmerstein, later Recke-Volmerstein. Lucia von Ovelacker was abbess of Herdecke Abbey from 1526 to 1542. The estate covered 169 hectares, and seven farms and fourteen cottages in the parish of Boele owed it tithes.

Nothing of the manor remains above ground: the ruins lie about 150 metres south-east of the Koepchenwerk, on the bed of the Hengsteysee. The site can only be viewed from the shore or the water, not entered. The lake was created after the Ruhrverband bought the land in 1919.

The manor house burned down in 1857 and was never rebuilt; only the farm buildings were leased out afterwards. In 1919 the Ruhrverband bought the land to build the Hengsteysee, and the remains of the knight's seat now lie about 150 metres south-east of the Koepchenwerk on the lake bed.