Fredrikstad is a city and municipality in Østfold county, Norway. The administrative centre of the municipality is the city of Fredrikstad. The city of Fredrikstad was founded in 1567 by King Frederick II, and established as a municipality on 1 January 1838. The rural municipality of Glemmen was merged with Fredrikstad on 1 January 1964. The rural municipalities of Borge, Onsøy, Kråkerøy, and Rolvsøy were merged with Fredrikstad on 1 January 1994.