Lusatia is a historical region in Central Europe, territorially split between Germany and Poland. Lusatia stretches from the Bóbr and Kwisa rivers in the east to the Pulsnitz and Black Elster rivers in the west, and is located within the German states of Saxony and Brandenburg as well as in the Polish voivodeships of Lower Silesia and Lubusz. Major rivers of Lusatia are the Spree and the Lusatian Neisse, which defines the border between Germany and Poland. The Lusatian Mountains of the Western Sudetes separate Lusatia from Bohemia in the south. Lusatia is traditionally divided into Upper Lusatia, the hilly southern part, and Lower Lusatia, the flat northern part.

The Spree is, with a length of approximately 400 kilometres (250 mi), the main tributary of the River Havel. The Spree is much longer than the Havel, which it flows into at Berlin-Spandau; the Havel then flows into the Elbe at Havelberg. The river rises in the Lusatian Highlands, that are part of the Sudetes, in the Lusatian part of Saxony, where it has three sources: the historical one called Spreeborn in the village of Spreedorf, the water-richest one in Neugersdorf, and the highest elevated one in Eibau. The Spree then flows northwards through Upper and Lower Lusatia, where it crosses the border between Saxony and Brandenburg. After passing through Cottbus, it forms the Spree Forest, a large inland delta and biosphere reserve. It then flows through Lake Schwielochsee before entering Berlin, as Müggelspree (pronounced [ˈmʏɡl̩ˌʃpʁeː] ).