The island was named by Wilhelm August Graah after Skjoldungen or Skioldungen, a honorific title for the successors of legendary King Skjold to the ancient Danish throne in Norse mythology.
Skjoldungen is a coastal island in the southeastern shores of Greenland. It is located between two fjords, the Southern Skjoldungen Fjord (Danish: Sonder Skjoldungesund; Greenlandic: Inugsuarmiut), to the southwest, and the Northern Skjoldungen Fjord (Danish: Nordre Skjoldungesund) to the northeast between Skjoldungen and one of the arms of the Thorland Peninsula. The Morke Sound (Danish: Mørkesund) is a 700 metres (2,297 feet) wide sound that joins both fjords in the NW, separating the island from the mainland.
The island stretches 49 kilometres (30 miles) in a NE/SW direction. Its highest point is Azimuthbjerg, a 1,738 m high ultra-prominent peak at the NW end of the island. Skjoldungen's maximum width is 14 kilometres (9 miles). Skjoldungen Island has a rugged terrain, which includes the Skjoldmøen, Bjarje and Hjalte glaciers and the Gedebukken, Pandebrasken, Skuren and Sfinksen nunataks. The southern part divides into two peninsulas jutting southeastwards, the Roar Peninsula (Danish: Roar Halvø) and the Helge Peninsula (Danish: Helges Halvø). Skjoldungen's southernmost headland is Cape Niels Juel, a narrow cape of reddish-brown rock at the end of the Helge Peninsula. 3.5 kilometres (2 miles) long Anarnitsoq island lies just to the west of the cape.
Since the eastern coast of Greenland was inhabited by Paleo-Eskimo people around 4,000 years ago, the Skjoldungen Fjords were likely inhabited or visited by nomadic hunters. At the Qoornoq site, located on a small headland by the shore of the Southern Skjoldungen Fjord, there are archaeological remains of later historical periods. These include Thule culture graves indicating that Inuit people lived on the island after the 13th century.
There are remains of relatively recent abandoned Inuit dwellings inside the fjord on Skjoldungen's western shore. These date back to 1938 when one hundred and fifty Inuit from Ammassalik were convinced by the Danish authorities to settle in this large island. During World War II a weather station was built and run by the Allies on Skjoldungen, as well as another one on Cape Adelaer further south down the coast at 61°50′N 42°5′W / 61.833°N 42.083°W / 61.833; -42.083. The inhabitants of the Inuit settlement were relocated in 1965 following a nationwide program to concentrate the population of Greenland in a few larger towns.
Currently the island is a popular destination with tourists on cruise ships to Greenland owing to its impressive landscapes.