Moss is a coastal town and a municipality in Østfold county, Norway. The administrative centre of the municipality is the town of Moss. The city of Moss was established as a municipality on 1 January 1838 (see formannskapsdistrikt). The rural municipality of Jeløy was merged with the city on 1 July 1943.

Its administrative district covers areas east of the town, such as the island of Dillingøy in the lake Vansjø. Parts of the town are located on the peninsula of Jeløy. Moss city has 30,723 inhabitants (2012).

The Old Norse form of the name was Mors. It may be derived from an old root mer- which means to "divide" or "split".

The adjacent topography shares similar etymology:

Archeological finds suggest that there were settlements in the area more than 7,000 years ago and continuously through the Iron Age, Viking Age, through to modern times. During the Viking era, the place was known as Varna (forne, vorne, front-protection?) and was the site of a cooperative for battleships held by local warlords on behalf of the king.

The first literary reference to the name Mo(u)ſs(ß) is from Bishop Eystein Aslaksson's Red book (NRA AM fol. 328) from 1396, and by then the town had become a commercial center with craftsmen and mills. By the 16th century, the town's port was significant enough to warrant its own customs official. Liquor distilleries became one of the dominant industries, and it was not until 1607, after the Reformation, that the town got its own church.

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