Hohensax is a ruined castle in the Sennwald municipality in the Swiss canton St. Gallen.
The castle was built around 1200 by the barons of Sax, and was destroyed in 1446.
In 1248, the castle passed to Ulrich von Sax, founder of the Sax-Hohensax line of the noble family.
The castle was plundered in a feud of 1393, and sold together with the villages of Sax and Gams to the dukes of Austria.
Address 9468, Switzerland
Coordinates 47°13'49.83" N 9°26'37.899" E