Rosa Luxemburg (also Rozalia Luxenburg; Polish: Róża Luksemburg; 5 March 1871 – 15 January 1919) was a German-Polish-Jewish Marxist theorist, philosopher, economist, anti-war activist, and revolutionary socialist who became a naturalized German citizen. She was, successively, a member of the Social Democracy of the Kingdom of Poland and Lithuania (SDKPiL), the Social Democratic Party of Germany (SPD), the Independent Social Democratic Party (USPD), and the Communist Party of Germany (KPD).
Due to her pointed criticism of both the Leninist and the more moderate social democratic schools of socialism, Luxemburg has had a somewhat ambivalent reception among scholars and theorists of the political left. Nonetheless, some have regarded Luxemburg and Liebknecht as martyrs of the socialist cause.