Appenzell Ausserrhoden, in English sometimes Appenzell Outer Rhodes, is one of the 26 cantons forming the Swiss Confederation. It is composed of twenty municipalities. The seat of the government and parliament is Herisau, and the seat of judicial authorities are in Trogen. It is traditionally considered a "half-canton", the other half being Appenzell Innerrhoden.

The 26 cantons of Switzerland are the member states of the Swiss Confederation. The nucleus of the Swiss Confederacy in the form of the first three confederate allies used to be referred to as the Waldstätte. Two important periods in the development of the Old Swiss Confederacy are summarized by the terms Acht Orte and Dreizehn Orte.