Jotunheimen (Norwegian pronunciation: [ˈjôːtʉnˌhæɪmn̩]; "the home of the Jötunn") is a mountainous area of roughly 3,500 square kilometres (1,400 sq mi) in southern Norway and is part of the long range known as the Scandinavian Mountains. The 29 highest mountains in Norway are all located in the Jotunheimen mountains, including the 2,469-metre (8,100 ft) tall mountain Galdhøpiggen (the highest point in Norway and Northern Europe). The Jotunheimen mountains straddle the border between Innlandet and Vestland counties (historically part of the old Oppland and Sogn og Fjordane counties).

Jotunheimen is very popular with hikers and climbers. The Norwegian Mountain Touring Association maintains a number of mountain lodges in the area, as well as marked trails that run between the lodges and others that run up to some of the peaks. The area has more than 50 marked trails, ranging from shorter hikes to multi day trails.

Mountaineering in Jotunheimen was pioneered in the late 19th century and early 20th century by British mountaineers William Cecil Slingsby, Harold Raeburn, and Howard Priestman, as well as Norwegian mountaineers such as Kristian Tandberg, George Paus and Therese Bertheau. Slingsby's 1904 book Norway, the Northern Playground contributed greatly to popularizing mountaineering in Jotunheimen among the international mountaineering community.

The image from Gjende shows a cliff trailing down into the lake. At its base there is a popular guest house called Memurubu. The picture is taken from Gjendesheim, a starting point for hiking into the mountain range. There is a very popular trail along Besseggen that follows the edge of the mountainous range to the right, which it is named after.

There is a National Tourist Route, the Sognefjell Road, from Skjolden to Lom, as well as another road, the RV 51, from Gol to Vågåmo through the special area of Valdresflya.

Originally there was no common name for this large mountainous area. However, in 1820, the Norwegian geologist and mountaineer, Baltazar Mathias Keilhau proposed the name Jotunfjeldene "the mountains of the Jotnar" (inspired by the German name Riesengebirge). This was later changed to Jotunheimen by the poet Aasmund Olavsson Vinje in 1862 – this name/form was directly inspired by the name Jötunheimr in Norse mythology.

Jotunheimen is a residual mountain area, which is a mass of rock that has remained in place as the surrounding relief has been eroded. The tops of Dovrefjell and Jotunheimen and other parts of southern Norway are the few remnants of a formerly flat surface that existed in Norway prior to uplift. This surface is now largely eroded and warped. The said erosion formed a series of steps and it is from the highest of these steps that Jotunheimen rise.

The characteristic mountain landforms in Jotunheimen have been sculptured by glacial geomorphology during the Pleistocene, especially during its last glacial period. Whereas the Scandinavian Ice Sheet covered most of Fennoscandia, some mountain peaks of Jotunheimen were not covered by glaciers and remained as Nunatak. Galdhopiggen, Glittertinden or Store Lauvhøi are examples. Towards the west, the Scandinavian Ice Sheet disintegrated in several glacier tongues and caused the formation of the Norwegian Fiords.