Schloss Brunn, Water castle in Brunn, Bad Fischau-Brunn, Austria

Schloss Brunn is a three-winged, two-storey building with a prominent round tower, the remnant of a 14th-century water castle, at Schlossplatz 1 in the Brunn an der Schneebergbahn district of Bad Fischau-Brunn. The moat was replaced by a garden after the fire, and parts of a horse-chestnut avenue survive.

The castle came under the ownership of the Teuffenbach family in the 14th century and became a fief of Styrian rule during the 15th century. Early 18th century brought substantial renovations that modernized the building's appearance and surroundings.

The name Brunn refers to the village where the castle stands, today part of Bad Fischau-Brunn. Prince Paul I. Esterházy laid out a garden on the site of the former moat after the fire, and sections of a horse-chestnut avenue he had planted survive. The building is a listed monument recorded in the Dehio handbook of Lower Austrian art monuments.

The castle is surrounded by hiking trails that connect it to neighbouring areas in the Wiener Neustadt-Land region. Visitors should wear comfortable shoes, as the terrain around the grounds varies in slope and path conditions.

The round tower at the centre of the main facade is the surviving core of the 14th-century water castle, predating the 1708–1711 rebuild by Prince Paul I. Esterházy. Parts of the horse-chestnut avenue he had planted along the former moat still stand.