Østfold (öst`fôl'), county (1995 pop. 239,371), 1,614 sq mi (4,180 sq km), SE Norway, between the Oslofjord in the west and the Swedish border in the east. Moss is the capital. The county's productive farms produce much grain, vegetables, and dairy goods. The area around the lower Glåma River is one of the important industrial centers in Norway, producing ships, chemicals, rubber, and processed food. Timber is floated down the Glåma from the Østerdalen valley for processing. The region of Østfold has been important in the cultural and military history of Norway and includes numerous prehistoric remains.