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 (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. Along with neighboring Sarpsborg, Fredrikstad forms the fifth largest city in Norway: Fredrikstad/Sarpsborg. As of 1 January 2013, according to Statistics Norway, these two municipalities have a total population of 128,916 with 75,583 in Fredrikstad and 53,333 in Sarpsborg.
Fredrikstad was built at the mouth of Glomma as a replacement after Sarpsborg (15 kilometres (9 miles) upstream) was burned down by the Swedes. Almost half the population of Sarpsborg stayed behind, and rebuilt their old town at its original site.
The city centre is on the west bank of the Glomma, while the old town on the east bank is Northern Europe's best preserved fortified town.
Fredrikstad used to have a large sawmill industry and was an important harbour for timber export, then later on shipbuilding, until the main yard was closed in the 1980s. The main industries are currently various chemical plants and other light industry.
In 2005, Fredrikstad was the final host port for the Tall Ships' Race, attracting thousands to the city.