Burg Hermannstein, Medieval castle in Wetzlar, Germany.

Burg Hermannstein stands on the Schwarzenberg above Wetzlar-Hermannstein. Its upper castle, built from the late 14th century, is modelled on French donjons: a tall round tower of rough light brown and grey stone with a flat top and small rectangular windows. A lower wall section on the left has a large open archway, and two rectangular chimneys rise from the roofline.

Landgrave Hermann II of Hesse began building the castle around 1377 on Solms territory to counter Count Johann IV of Solms-Burgsolms, who had seized Wetzlar; lime and stone were delivered that July. The 1379 peace treaty gave the site to Hesse. In 1481 Johann Schenk zu Schweinsberg bought the dilapidated castle for 900 gulden and rebuilt it, adding the Unterburg; his descendants formed the Hermannsteiner line. Sold to Buderus AG in 1961, it became private property in 1965.

The castle gave its name to the Hermannstein line of the Schenck zu Schweinsberg family, who resided there from 1481 and usually wrote their name with a single "k". The surrounding village of Hermannstein, now a Wetzlar district, grew below the castle.

Burg Hermannstein is private property: it was bought in 2010 by a Dutch couple, Emile and Heidy van Duren, and from February 2012 their staff partly restored and lived in it. The castle is not open to visitors, so the grounds and interior cannot be toured; the complex is seen from outside, above the Hermannstein district of Wetzlar.

The castle is private property, bought in 2010 by the Dutch couple Emile and Heidy van Duren; since February 2012 their staff have partly lived in and restored it. A 1631 copper engraving by Daniel Meisner still shows the castle intact, before it fell into ruin.