Sweden-Finland is a term sometimes used for the Swedish Kingdom between the Kalmar Union and the Napoleonic wars, or the period from the 14th to the 18th century. In 1809 the realm was split and the eastern half came to constitute the semi-autonomous Grand Duchy of Finland, in personal union with Imperial Russia.

Although the term has didactic merits, for instance when used in conjunction with the terms Denmark-Norway and Sweden-Norway, it is potentially misleading – and contradicting contemporary usage. Finland (proper), as understood from the middle ages and forth, was merely one of the provinces of Sweden; while what today constitutes the Republic of Finland was then a set of provinces comprising the eastern part of Sweden proper, of which the for farming more suitable southern part was usually called Österland ("the Eastern land"). Gradually, that term fell from use, and finally in the 18th century, after the whole of present-day Finland had been twice occupied by Russian forces (1714–21 and 1742–43), "Finland" was commonly used for the land of the Finns, where the common people spoke Finnish language.

The northern and eastern border of "Finland" was established first with the Russo–Swedish peace treaty of 1809. The North was sparsely populated, but Finnish mothertongue dominated in large areas also on the western, Swedish, side of the new border. In Sweden, however, the Finnish speakers were a minority confined to the northern and western peripheries, that in the ensuing centuries has assimilated and become Swedish speakers.

See also

• History of Sweden
• History of Finland