Herisau is a metropolis in the canton of Appenzell Ausserrhoden in Switzerland.
It is sited in the prime zone of eastern Switzerland in 1537 and has developed into an important centre of trade. The total population is of 15,600 according to the 2002 census and extends over an area of 25.17 km². Herisau is the place of the canton's government and parliament. It was the capital of the Canton Säntis in 1803.

The year of 1084 Herisau saw its destruction due to the battles around the monastery in St. Gallen. It was demolished again in 1248 and 1249 by the monastery to establish their loyalty. In 1401 Herisau united to form an alliance with new places in Appenzell. In 1518 Herisau managed to liberate itself from the monastery and the town hall was rebuilt in 1601.