Burg Schwartzenburg, Medieval castle in Stolberg, Germany.

Burg Schwartzenburg was a moated castle in Dorff, now part of Stolberg. Its main castle was a large rubble-stone complex with four semicircular corner towers with corbelled crenellated parapets, surrounded by a moat, and rising two storeys with small rectangular windows. A bailey stood on the wider grounds. Today only the entrance gate remains, giving an idea of how the whole complex was built.

Reinhard Soldener von Schwartenbergh, a vassal of the Imperial Abbey of Kornelimünster, built the water castle around 1400; a monastery document of 28 October 1404 names him. In 1688, during the Palatinate War of Succession, French mercenaries besieged it for several days; Adrian von der Bylandt zu Holtheide and many defenders died, and the castle was burned to its foundations. Its stones were later quarried by villagers, and only the entrance gate survives.

Locals call the ruin Schwazermesch, and stories about it are passed down in Dorff dialect. The name passed from the Schwartzenberg family to the Voss and later the Bylandt families through marriages, and the site has belonged to the Gatz, von Agris and von Hoegen families for generations.

Only the entrance gate of the former water castle survives, so there is no interior or museum to visit; the remains stand in the village of Dorff, part of Stolberg. The gate can be viewed from the outside, and the surrounding area is crossed by walking and hiking trails. The site belongs to private owners, the Gatz, von Agris and von Hoegen families, so access to the grounds depends on their permission.

Only the entrance gate survives today; the rest of the main castle was burned to its foundations in 1688 and its stones were long reused by villagers from Dorff and the surrounding area as a quarry. Locals know the site in their dialect as "Schwazermesch".