Sarpsborg (pronounced [ˈsɑ̀ʂbɔr] or [ˈsɑ̀rpsbɔrɡ]), historically Borg, is a city and municipality in Viken county, Norway. The administrative centre of the municipality is the city of Sarpsborg.
Sarpsborg is part of the fifth largest urban area in Norway when paired with neighbouring Fredrikstad. As of 1 January 2018, according to Statistics Norway these two municipalities have a total population of 136,127 with 55,840 in Sarpsborg and 81,278 in Fredrikstad.Borregaard Industries is, and always has been, the most important industry in the city. The city is also the home of Borg Bryggerier, part of the Hansa Borg Bryggerier, which is Norway's second largest brewery-group.