Os is a municipality in the county of Hordaland, Norway. Os was made a municipality in 1837 and until 1854 included neighbouring Fusa and Samnanger. The name Os comes from the Os vicarage which, in turn, was named after the Os river whose mouth runs through the centre of Os.
In 1999, the right-wing Progressive Party won the election, and Terje Søviknes became mayor making him the first FrP politician to hold that position. Since then, twelve other municipalities have got a FrP mayor.
Os has a tradition for small boat building. The traditional boat of Os is Oselvaren, a small wooden boat. This boat is the official seal of Os. These boats have been used for everyday work and for travelling to church. These boats were either sail boats or one could row. They still build these boats the traditional way in Os, and tourists are able to visit and watch them work.
The famous violinist Ole Bull built his summerhouse in Os, on an island named Lysøen. This building was inspired by his travels, especially his travels to the Middle East.
Lysøen was originally owned by Lysekloster monastery, the ruins of which still stand and are frequently visited.