K�snacht is first mentioned in 1188 as de Cussenacho.
Earliest findings of settlement date back to the stone age. There are also findings from the Bronze Age. During Roman times, a mansion was located on the commons. It was called fundus Cossiniacus which is probably the origin of the name of K�snacht. In the 7th century the name was recorded as Chussenacho. The coat of arms shows a golden cushion on a red background. It is probably a derivate of the coat of arms of the aristocrats of K�ssnacht am Rigi.
In the Middle Ages, the land was governed by the people of Regensberg who lived in the castle of Wulp in K�snacht. After 1531 K�snacht was governed by Zurich.
Like most other municipalities along Lake Z�rich, K�snacht started to become a suburb of the city of Z�rich with the development of the railway link in 1896.
The psychiatrist Carl Jung had his clinic in K�snacht, which attracted patients from all over the world. Thomas Mann lived in K�snacht between 1933 and 1939, after he was forced to leave Germany by the Nazis. Among the most famous residents of the town is Tina Turner
