Lower Lusatia (German: Niederlausitz [ˈniːdɐˌlaʊzɪts]; Lower Sorbian: Dolna Łužyca [ˈdɔlna ˈwuʒɨtsa]; Upper Sorbian: Delnja Łužica [ˈdɛlnʲa ˈwuʒitsa]; Polish: Łużyce Dolne; Czech: Dolní Lužice) is a historical region in Central Europe, stretching from the southeast of the German state of Brandenburg to the southwest of Lubusz Voivodeship in Poland. Like adjacent Upper Lusatia in the south, Lower Lusatia is a settlement area of the West Slavic Sorbs whose endangered Lower Sorbian language is related to Upper Sorbian and Polish.

This sparsely inhabited area within the North European Plain (Northern Lowland) is characterised by extended pine forests, heathlands and meadows. In the north it is confined by the middle Spree River with Lake Schwielochsee and its eastern continuation across the Oder at Fürstenberg to Chlebowo. In the glacial valley between Lübben and Cottbus, the Spree River branches out into the Spreewald ("Spree Woods") riparian forest. Other rivers include the Berste and Oelse tributaries as well as the Schlaube and the Oder–Spree Canal opened in 1891.

In the east, the Bóbr river flows from Łagoda via Krzystkowice down to the historic town of Żary forms the border with the lands of Lower Silesia. In the west the course of the upper Dahme River down to Golßen separates it from the former Electoral Saxon lands of Saxe-Wittenberg. Between Lower and Upper Lusatia is a hill region called the Grenzwall (literally "border dike", although it is in fact a morainic ridge), the eastern continuation of the Fläming Heath. In the Middle Ages this area had dense forests, so it represented a major obstacle to civilian and military traffic. Today it is roughly congruent of the border between Brandenburg and the state of Saxony.

In the course of much of the 19th and the entire 20th century, Lower Lusatia was shaped by the lignite (brown coal) industry and extensive open-pit mining, by which more than 100 of the region's villages—many of them within the Sorbian settlement area—were damaged or destroyed, especially by order of East German authorities. While this process is still going on, most notably around Jänschwalde Power Station, run by EPH, some now exhausted open-pit mines are being converted into artificial lakes, in the hope of attracting tourism, and the area is now referred to as the Lusatian Lake District (Lausitzer Seenland).

Today the area comprises the Brandenburg districts of Oberspreewald-Lausitz and Spree-Neiße with the unitary authority of Cottbus, as well as parts of Elbe-Elster, Dahme-Spreewald, and Oder-Spree. Important towns beside Cottbus and the historic capitals Lübben and Luckau include Calau, Doberlug-Kirchhain, Finsterwalde, Forst, Guben/Gubin, Lauchhammer, Lübbenau, Senftenberg, Spremberg, Vetschau, and Żary.

Since 1945, when a small part of Lusatia east of the Oder–Neisse line was incorporated into Poland, Żary has been touted as the capital of Polish Lusatia.

Up to the late medieval times, the region was known just as Lusatia (proper), gaining the Lower designation in the 15th century, when the neighboring region to the south (Land of Bautzen, previously the land of Slavic Milceni) became known as the Upper Lusatia. In early medieval sources, Lusatia (proper) was initially mentioned as land of Slavic Lusatians, and later as a march (frontier region). Thus in the second half of the 10th century, Widukind's Chronicle mentions Lusiki, while Thietmar's Chronicle from the beginning of the 11th century mentions Lusici or Lusizi, and also Luzici or Luidizi.

According to those sources, sometime during the early 960s, Slavic Lusatians were attacked by count Gero I, commander of the Saxon frontier regions, who forced them to subdue and pay tribute to German king and emperor Otto I (936-973). In 983, the Slavic revolt broke out in neighboring regions to the north, but German rule over Slavic Lusatians and their southern neigbors Milceni endured until 1002, when their regions were captured by the Polish duke Bolesław I the Brave, who took the town of Bautzen (Upper Sorbian: Budyšin) and all regions up to the river Elbe, and also captured the city of Meissen (Upper Sorbian: Mišno) with all territories up to White Elster river.