Roman Catholic Diocese of Finland
Diocese of Finland was the predecessor of the Catholic diocese of Turku. It was probably founded in the 12th century, but the Bishop of Finland is first mentioned only in 1209. Diocese seems to have been independent on secular powers until the so-called Second Swedish Crusade in 1249. The diocese was renamed as the Diocese of Turku latest in 1259 by when it had been assimilated to the Swedish set of dioceses.
The see was located in Nousiainen at least in 1234 when Bishop Thomas signed a letter there. The bishop had received papal approval for the transfer of the see in 1229, but it is not known if the transfer actually took place. If the see had been located somewhere else before, the location is unknown. The see was later moved to Koroinen close to the current cathedral of Turku, probably soon after the Swedish conquest in 1249.
Bishops of Finland are usually included in the list of Bishops of Turku.