Eidsberg was a municipality in Østfold county, Norway. The administrative centre of the municipality was the town of Mysen. In 2020, Eidsberg was absorbed into the Indre Østfold municipality.

Eidsberg was established as a municipality on 1 January 1838 (see formannskapsdistrikt). The town of Mysen was separated from Eidsberg to form a municipality of its own on 1 July 1920, but it was merged back into the municipality of Eidsberg on 1 January 1961.

The municipality (originally the parish) was named after the old Eidsberg farm (Old Norse: Eiðsberg) because the first church was built here. The first element is the genitive case of eið 'path around a waterfall' and the last element is berg 'mountain'. Prior to 1847, the name was spelled Edsberg.

The coat-of-arms was from modern times. It was granted on 16 March 1962. The arms show a bear, which is taken as a symbol for Arnbjørn Jonsson, who lived in Eidsberg. The bear is canting for Bjørn (Norwegian: bear). He was a well-known warrior during the civil war era under King Håkon Håkonsson, until his death in 1240.

Number of minorities (1st and 2nd generation) in Eidsberg by country of origin in 2017

Ancestry	Number
Poland	398
Iraq	178
Lithuania	140
Bosnia-Herzegovina	99
Sweden	81
Kosovo	65
Russia	58
Somalia	47
Pakistan	40
Denmark	36

• Media related to Eidsberg at Wikimedia Commons
• Østfold travel guide from Wikivoyage
• The dictionary definition of Eidsberg at Wiktionary
• Municipal fact sheet from Statistics Norway