Werdenberg was a county of the Holy Roman Empire, within the Duchy of Swabia, situated on either side of the Alpine Rhine , including parts of what is now St. Gallen (Switzerland), Liechtenstein, and Vorarlberg (Austria). It was partitioned from Montfort in 1230. In 1260, it was divided into Werdenberg and Sargans.

It is named for Werdenberg Castle, today located in the municipality of Grabs in the Swiss Canton of St. Gallen , seat of the counts of Werdenberg (Werdenberger), The family was descended from count Hugo II of Tübingen (d.