The Glomma (Glåma) is the longest river which lies within the borders of which Nordic country?

The Nordic countries are a geographical and cultural region in Northern Europe and the North Atlantic, where they are most commonly known as Norden (literally "the North"). The term includes Denmark, Finland, Iceland, Norway and Sweden and their territories.

The Glomma (Glåma) is Norway's longest and most voluminous river. It has a drainage basin that covers fully 13% of Norway's surface area, all in the southern part of the country.

It rises in a series of small lakes and streams that drain into Aursunden (lake) about 80 miles (130 km) southeast of Trondheim, near the Swedish-Norwegian border.

It flows out of the lake southward through Østerdalen (Eastern Valley) to Kongsvinger, then westward and southwestward into Øyeren (lake).

It continues southward to Sarpsborg and enters Oslo Fjord at Fredrikstad after a course of 372 mi ( 599 km). Fredrikstad straddles the river where it meets the Skagerrak, about 12mi (20 km) from the Swedish border.

It drains an area of 16,236 sq mi (42,051 sq km) with its chief tributaries being the Atna, Rena, and Vorma. Fredrikstad/Sarpsborg forms the 5th largest city in Norway.

The Glomma flows through Norway’s timber forests to Sarpsborg, which has sawmills and paper mills to handle the logs that are floated downstream. The river is a major source of hydroelectric power. Flumes and artificial channels bypass the falls and power plants, and the Glomma is navigable from its mouth up to the Sarpsfoss (Sarps Falls) at Sarpsborg.