Schwarzenbach Castle, Medieval castle in Jonschwil, Switzerland

Schloss Schwarzenbach stands elevated on the right bank of the Thur in the village of Schwarzenbach, part of Jonschwil. The complex consists of the former keep, the oldest part from Rudolf of Habsburg's time after 1282, the former granary from the 17th century, and remnants of the ring wall. The gate structure was added in the 20th century and is not authentic.

Schwarzenbach was first documented on 16 March 779. In the 12th century the local noble family built a small fort north of the old mill to guard the Thur crossing on the road between Wil and St. Gallen; the line died out around 1250. Count Rudolf of Habsburg, who took over the advocacy of St. Gallen Abbey in 1273, had a larger castle with the surviving keep built above the Thur after 1282 and founded the town of Schwarzenbach beside it. In 1483 castle and lordship passed to the Prince-Abbey of St. Gallen, which made it the seat of the Obervogtei Niederamt.

The name Schwarzenbach means "black brook"; the bailiwick's coat of arms showed a black stream with gold ribbons on silver. The chapel was later used as a laundry and sheep pen, and a spinning mill operated in the granary. The gate structure dates only from the 20th century.

The castle stands on the right bank of the Thur in Schwarzenbach, within the municipality of Jonschwil. It is a private property that was offered for sale as a luxury real estate in 2009, so access is not guaranteed; visitors should check in advance. The gate structure dates from the 20th century and is not part of the original medieval complex.

The gatehouse is not medieval: it was added in the 20th century. The ring wall was largely demolished in the mid-19th century, and its stones were reused for the railway bridge over the Thur. The chapel once served as a laundry and sheep pen.