Hermiswil is a former municipality in the Oberaargau administrative district in the Canton of Bern in Switzerland . On 1 January 2016 it merged into the municipality of Seeberg .

Hermiswil is first mentioned in 1289 as Hermanswile.

During the 13th and 14th centuries, the Hermiswil area had been granted by the Kyburg family to the vom Stein family. In 1466 the city of Solothurn inherited all the vom Stein holdings, which included Hermiswil. Following the Wyniger Vertrag, of 1665, the village was given to Bern.