Abstract The earliest history of the Swedish Realm’s northern regions has long been contested in historiography. This article primarily analyses views in seventeenth-century Swedish historiography concerning the origins of Finns in this region, in terms of source usage and ethnic identities. Gothicist views, emphasizing Swedish greatness were based on biblical notions of a postdiluvial settlement, linking sources from classical antiquity to Sweden via etymological comparisons. Combined with a reliance on Icelandic sagas and the uncritical use of secondary sources, these notions gave rise, among others, to the idea of an ancient, partially Finnish, Amazon warrior realm in Ostrobothnia. Conceptions surrounding the origins of Birkarl tax coll...