Old Finland (Vanha Suomi in Finnish) is a name used for the areas that Sweden lost to Russia in the Great Northern War and in the Hats' Russian War. Old Finland was joined to the autonomous Grand Duchy of Finland in 1812.

• In the Peace Treaty in 1721, that concluded the Great Northern War, Sweden had to cede the Käkisalmi County and Wiburg/Viipuri County.

• In the Peace Treaty in 1743 Sweden had to cede the areas in southern Karelia east of the Kymi river and around Savonlinna.

The Russian ruler guaranteed religion, properties, laws and privileges of the inhabitants of these territories. However, in small details, circumvention occurred, as Russian administrators and military were unfamiliar with Swedish system, and were used to a different system with its enslaved peasants, serfdom.

That guarantee froze the situation, thus legal developments in Sweden were not introduced to these areas: The Viipuri and Käkisalmi territory did not adopt the 1734 General Law of Sweden (though Hamina, Lappeenranta and Savonlinna, then yet Swedish, of course did), and new Constitutions of Gustav III were out of question in the entire area.

The territories enjoyed a sort of autonomy and much particularism, since the Russian rulers applied similar principles here as in Baltic Provinces. The administration resembled a bunch of German principalities, rather than a Russian province.

These areas were later referred to as Old Finland and from the beginning of the year 1812 they were incorporated in the Grand Duchy of Finland. Basically, the population in these provinces came to the same legal system as the Grand Duchy, including its Constitution and General Law, although some privileges took time to adapt, and so-called donated estates (owned by Russian noblemen) in Karelia were a headache that was resolved slowly by monetary compensations from the Grand Duchy's Treasury.