First Swedish Crusade

The First Swedish Crusade was a possibly mythical military expedition around 1150 that has traditionally been seen as the conquest of Finland by Sweden, with pagan Finns converting to Christianity. According to the legend, the crusade was conducted by King Eric IX of Sweden. Bishop Henry of Uppsala accompanied him and remained in Finland later to become a martyr there.

Academics debate whether this crusade actually took place. No archaeological data give any support for it, and no surviving written source describes Finland under Swedish rule before the end of the 1240s. Furthermore, the diocese and bishop of Finland are not listed among their Swedish counterparts before the 1250s.

At the time, leading the leiðangr was the responsibility of the jarl. This gave rise to a theory that Eric conducted the expedition before he became king or pretender to the throne. Legends give no year for the expedition, and attempts to date it to an exact year in the 1150s are all much later speculations. All that is known about king Eric and bishop Henry is that they most probably held important positions in Sweden some time in the mid-12th century.

The Swedish bishop normally involved in the eastern campaigns was the Bishop of Linköping, not the Bishop of Uppsala.

The mid-12th century was a very violent time in the northern Baltic sea, with Finns and Swedes in frequent conflicts with Novgorod; there may have been a Swedish military expedition against Finland. In the First Novgorod Chronicle there is a story that in 1142 a Swedish "prince" and bishop accompanied by a fleet of 60 ships plundered just three Novgorodian merchant vessels somewhere "on the other side of the sea", obviously being after something more important.