Olaf I of Norway in the context of Sigmundur Brestisson

The term Norwegian Realm (Old Norse: *Noregsveldi, Bokmål: Norgesveldet, Nynorsk: Noregsveldet) and Old Kingdom of Norway refer to the Kingdom of Norway's peak of power in the 13th century after a long period of civil war before 1240. The kingdom was a loosely unified nation including the territory of modern-day Norway, modern-day Swedish territory of Jämtland, Herjedalen, Ranrike (Bohuslän) and Idre and Särna, as well as Norway's overseas possessions which had been settled by Norwegian seafarers for centuries before being annexed or incorporated into the kingdom as 'tax territories'. To the North, Norway also bordered extensive tax territories on the mainland. Norway, whose expansionism starts from the very foundation of the Kingdom in 872, reached the peak of its power in the years between 1240 and 1319.

At the peak of Norwegian expansion before the civil war (1130–1240), Sigurd I led the Norwegian Crusade (1107–1110). The crusaders won battles in Lisbon and the Balearic Islands. In the Siege of Sidon they fought alongside Baldwin I and Ordelafo Faliero, and the siege resulted in an expansion of the Kingdom of Jerusalem. Leif Erikson, an Icelander of Norwegian origin and official hirdman of King Olaf I of Norway, explored America 500 years before Columbus. Adam of Bremen wrote about the new lands in Gesta Hammaburgensis ecclesiae pontificum (1076) when meeting Sweyn I of Denmark, but no other sources indicate that this knowledge went farther into Europe than Bremen, Germany. The Kingdom of Norway was the second European country after England to enforce a unified code of law to be applied for the whole country, called Magnus Lagabøtes landslov (1274).

Sigrid the Haughty (Old Norse: Sigríðr (hin) stórráða; Swedish: Sigrid Storråda) is a Scandinavian queen appearing in Norse sagas. Sigrid is named in several late and sometimes contradictory Icelandic sagas composed generations after the events the stories describe, but there is no reliable, historical evidence attesting to the veracity of her depiction in those tales. She is reported by Heimskringla to have been the wife of Eric the Victorious of Sweden, as being sought after by Olaf Tryggvasson, and then married to Sweyn Forkbeard of Denmark. In other writings, however, author Snorri Sturluson says that Sweyn the Dane was married not to Sigrid but some other woman.

It is unclear if the figure of Sigrid was a real person. Some recent scholars identify her with a documented Polish wife of Eric and perhaps Sweyn mentioned by medieval chroniclers and referred to as 'Świętosława' by some modern historians, but the potential husbands attributed to Sigrid lived over a wide date range and other modern scholars believe Sigrid may be an amalgamation of several historical women.