Herisau is a municipality and the capital of the canton of Appenzell Ausserrhoden in Switzerland.

It is the seat of the canton's government and parliament; the judicial authorities are situated in Trogen.

The central hamlet and the houses around the central square, the Protestant church of 1580, the houses Wetter and zur Rose (both 1737), the hamlet Schwänberg and the government building with the state archive are listed as heritage sites of national significance.

Of the rest of the land, 15.5% is settled (buildings or roads) and the remainder (0.6%) is non-productive (rivers, glaciers or mountains).

[4] It consists of the village of Herisau and scattered hamlets as well as bedroom communities and industrial sections.

Most of the population (as of 2000[update]) speaks German (87.0%), with Serbo-Croatian being second most common ( 3.8%) and Italian being third ( 3.4%).

[7] The age distribution, as of 2000[update], in Herisau is; 1,194 people or 7.5% of the population are between 0–6 years old.

The wettest month is July during which time Herisau receives an average of 167 mm (6.6 in) of precipitation.

The driest month of the year is February with an average of 82 mm (3.2 in) of precipitation over 13.9 days.