The House of Munsö (), also called the House of Björn Ironside (Swedish: ), the House of Uppsala (Swedish: ) or simply the Old dynasty (Swedish: ), is the earliest reliably attested royal dynasty of Sweden, ruling during the Viking Age. None of the names suggested for the dynasty are universally accepted and most are problematic; the name "House of Munsö" derives from a questionable and speculative theory that they would have ruled from the island of Munsö and the name "House of Björn Ironside" derives from the supposed founder of the dynasty, Björn Ironside, who is often seen as a legendary, rather than historical, figure. A long and elaborate sequence of kings of the Munsö dynasty can be found in 12th and 13th century Icelandic sagas, but the sagas are overwhelmingly considered unreliable, with the kings that appear in them seen as legendary figures. The sequence of kings in the sagas is contradicted by more contemporary German sources such as the 9th century writings of Rimbert and the 11th century work of Adam of Bremen. Etymology and historiography Due to a lack of preserved sources, little concrete information is known of Swedish kings during the Viking Age. Although long and elaborate king lists are provided by Icelandic sagas, sometimes contradictory mixtures of myths and poetry, and poems, these works (including texts such as Ynglinga saga, Hervarar saga, Ynglingatal and Langfeðgatal) are not considered reliable sources by modern scholars. Critically, a majority of them were written in the 12th to 13th century, centuries after the kings they described are supposed to have lived; what is genuine history and what is myth and legend is impossible to determine and everything contained in them must as such be regarded as legendary, if not fictional. The 12th and 13th centuries was a time when royal power was being consolidated in Norway, Denmark and Sweden and as such, king lists may have been created out of a political and social needs (i.e. justifying the rule of a royal dynasty), rather than a desire to tell genuine history. Many of Sweden's legendary kings would have preceded the Viking Age, but historical evidence of early geopolitics in Scandinavia suggests that larger political structures, kingdoms such as medieval Sweden, Norway and Denmark, did not form until the late Viking Age. The centralization of power under one monarch is believed to have resulted from, or at the very