Lusatia (German: Lausitz, Polish: Łużyce, Upper Sorbian: Łužica, Lower Sorbian: Łužyca, Czech: Lužice, Latin: Lusatia, rarely also referred to as Sorbia) is a historical region in Central Europe, 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. Lusatia's central rivers are the Spree and the Lusatian Neisse, which constitutes the border between Germany and Poland since 1945 (Oder–Neisse line). The Lusatian Mountains (part of the Sudetes), separate Lusatia from Bohemia (Czech Republic) in the south. Lusatia is traditionally divided into Upper Lusatia (the hilly southern part) and Lower Lusatia (the flat northern part).

The areas east and west along the Spree in the German part of Lusatia are home to the Slavic Sorbs, one of Germany's four officially recognized indigenous ethnic minorities (alongside Sinti and Roma, Frisians, and Danes). The Upper Sorbs inhabit Saxon Upper Lusatia, and the Lower Sorbs Brandenburgian Lower Lusatia. Upper and Lower Sorbian are spoken in the German parts of Upper and Lower Lusatia respectively, and the signage there is mostly bilingual. German and Sorbian-speakers were expelled from the regions east of the Lusatian Neisse in and after 1945, when the eastern part of Lusatia became Polish and was repopulated by Polish-speakers.

Lusatia is the theme of the Sorbian national anthem Rjana Łužica (Rědna Łužyca). The Lusatian Lake District (Lausitzer Seenland) is Europe's largest artificial lake district. The village of Herrnhut (Ochranow) is the seat of the Moravian Church. Muskau Park in Bad Muskau (Mužakow) and Łęknica is a UNESCO World Heritage Site. The Tropical Islands Resort, a large water park housed in the biggest free-standing hall in the world, is located in the north of Lusatia. The closest international airport to Lusatia is Dresden Airport in Klotzsche (Kłóčow).

The largest Lusatian city is Cottbus (Chóśebuz), other notable towns are the former members of the Lusatian League (the German/Polish twin towns of Görlitz (Zhorjelc) and Zgorzelec, Bautzen (Budyšin), Zittau (Žitawa), Lubań, Kamenz (Kamjenc), and Löbau (Lubij)), as well as Żary, the German/Polish twin towns of Guben (Gubin) and Gubin, Hoyerswerda (Wojerecy), Senftenberg (Zły Komorow), Eisenhüttenstadt (Pśibrjog), and Spremberg (Grodk).