Södermanland, locally Sörmland, sometimes referred to under its Latinized form Sudermannia or Sudermania, is a historical province on the south eastern coast of Sweden. It borders Östergötland, Närke, Västmanland and Uppland. It is also bounded by lake Mälaren and the Baltic Sea.

Östergötland is one of the traditional provinces of Sweden in the south of Sweden. It borders Småland, Västergötland, Närke, Södermanland and the Baltic Sea. In older English literature, the Latinized version Ostrogothia is also used. The corresponding administrative county, Östergötland County, covers the entire province and parts of neighbouring provinces.