[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.

For a consecutive list from then, the first Swedish king of whom anything definite is known is the 10th-century Eric the Victorious, though the information reported about him in different sources is scarce.

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.