Altstätten is a small historic rural town and a municipality in the district Rhine Valley, in the Canton of St. Gallen in Switzerland. It is located with some secure distance of about 5 kilometres (3.1 mi) west from the Alpine Rhine in the flat and wide St. Gall Rhine Valley, which also designates the border with Austria. It further gives access to the higher situated Appenzell to the west.

The official language of Altstätten is (the Swiss variety of Standard) German, but the main spoken language is the local variant of the Alemannic Swiss German dialect.