Fredrikstad (Norwegian: [ˈfrɛ̀drɪkstɑ] (listen); previously Frederiksstad; literally "Fredrik's Town") is a city and municipality in Viken 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 (see formannskapsdistrikt). 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.
The city straddles the river Glomma where it meets the Skagerrak, about 20 kilometres (12 mi) from the Sweden border. Along with neighboring Sarpsborg, Fredrikstad forms the fifth largest city in Norway: Fredrikstad/Sarpsborg.