[4] The securely attested Swedish rulers in the Viking Age, predecessors of the later line of Swedish kings, ruled from the religious and political center of Old Uppsala; though its history before the Viking Age is poorly attested, it is probable that Old Uppsala had been a political and religious center since the Migration Period.

[5] The earliest historically attested Swedish rulers are 9th-century petty kings from the Vita Ansgarii, an account written c. 870 by Rimbert partly concerning Saint Ansgar's visit to Svealand.

Eric's son Olof Skötkonung was the first king to be baptized in Sweden and is credited with founding a Christian kingdom.

He is often credited as the founder of modern Sweden,[11] and in 1544 he formally abandoned the previous elective monarchy in favor of hereditary succession.

[14] In 1980, the rule of succession was changed from agnatic to absolute primogeniture, to the benefit of Princess Victoria (born 1977), the current heir apparent.