Österland or Österlanden a historical land of Sweden. Österland, which literally means eastern lands, is the old name for Finland or what today geographically is the southern part of the Republic of Finland. It is bounded to the north by Eastern Norrland.
From early middle ages the Swedish Vikings had been settled on both sides of the Baltic sea. Following this long standing Swedish presence along the coast of southern Finland the kings of Svealand, in the 12th century and under influence from the Church, launched a crusade which resulted in the conquest of the entire Finland. The conquest took place at the same time as Sweden was united under one king and Österland was seen as a constituent part of the Swedish kingdom, and represented in the election of Swedish kings as early as 1362.
In 1581 the provinces of Österland was declared as the Archduchy of Finland by King John III of Sweden. It remained part of Sweden until the Finnish war of 1809, when it was ceded to Russia along with eastern Norrland.