Stahlberg Castle, Medieval castle ruins near Bacharach, Germany

Stahlberg Castle is a medieval ruin near Bacharach set high on a steep rocky outcrop above the Middle Rhine Valley. The partially preserved walls form the foundation of a former fortified structure with defensive towers and ditches.

Dendrochronological dating from 2005 places the construction of the whole complex between 1158 and 1168, probably commissioned by the Archbishops of Cologne to secure their estates, possibly as a counter-castle to Stahleck. In 1243 it passed as a fief to the Wittelsbach Counts Palatine, and from 1317 to 1353 it was pledged to the Archbishops of Trier. A second major building phase in the second quarter of the 14th century followed collapses of the rectangular keep and the south-western ring wall; the round keep was raised then, with smaller additions around 1470.

The castle chapel was dedicated to Saint Peter; its floor plan with a recessed apse and remains of the stair to the gallery are still visible. The site is owned by the Rheinischer Verein für Denkmalpflege und Landschaftsschutz, which opened it up in 1912 and has carried out conservation work since, including on the round bergfried and south-western wall from 2009 to 2013.

The steepest approach is the historic path from the Dorweiler Bach valley, where a long high retaining wall supports the route up to the gate; a modern wooden footbridge crosses the neck ditch in front of the core castle. The ruin lies above the Steeg district of Bacharach, between the Borbach and Dorweiler Bach valleys. The site has been cleared and secured since 1912, with work continuing since 2021.

The 2005 dendrochronological study dated the whole complex to 1158–1168, disproving earlier assumptions that the upper and lower castles were built at different times. The long high retaining wall that supports the steep access from the Dorweiler Bach valley is considered a technical work of the High Middle Ages without equal on the Middle Rhine.