The
parish of Os was established on 1 January 1838 as a
formannskapsdistrikt, the predecessor of today's municipalities. It originally encompassed all of the land surrounding the
Fusafjorden. In 1856, the eastern district of Os (across the fjord) was separated to form the new
Fusa Municipality. This left Os Municipality with 3,750 residents. In 1900, "Askviknes Barnehjem" (near
Hagavik) opened; it housed children of
romani/
tater descent; in the beginning the children's stay was something their families applied for; later children were introduced to the facility without consent of their families. On 1 January 1907, the northern part of the municipality was separated to form the new
Samnanger Municipality. This left Os Municipality with 3,188 residents. Historically, this municipality was part of the old
Hordaland county. Also on 1 January 2020, the new Bjørnafjorden Municipality became a part of the newly-formed
Vestland county (after
Hordaland and
Sogn og Fjordane counties were merged).
Name The municipality (originally the
parish) is named after the old
Os farm () since the first
Os Church was built there. The name is identical to the word which means "mouth of a river", referring here to the Oselva river.
Coat of arms The
coat of arms was adopted in 1949 and it was in use until 1 January 2020 when the municipality was dissolved. The
blazon is
"Gules, one large and six small roses over a rowboat Or". This means the arms have a red
field (background) and the
charge is a rowboat underneath a flower and six small stars surrounding the flower. The charge has a
tincture of
Or which means it is commonly colored yellow, but if it is made out of metal, then gold is used. The arms were adopted in 1949 after a local competition. Boat building has been an important industry in Os for a long time. The rowboat design was chosen to symbolize the
Oselvar boat which is commonly built and used in this area. The Oselvar is widely known for its good rowing and sailing properties. The roses in the coat of arms stand for the art of
rosemåling which has long been used for decorations in the area. The small roses in the design corresponded to the number of school districts in Os when the coat of arms was new. The municipality often includes a
mural crown over the shield. The arms were designed by Trygve Eriksen. ==Churches==