Marguerite Hélène Barbe Elisabeth Constantine Lion (28 February 1899 – 24 February 1989), known as Margo Lion, was a French chanteuse, parodist, cabaret singer and actress, best known for her role as Pirate Jenny in director G.W. Pabst's 1931 French language adaptation of Bertolt Brecht and Kurt Weill's Threepenny Opera (Die Dreigroschenoper).
She appeared in several French films until the early 1970s, including Docteur Françoise Gailland, L'Humeur Vagabonde, La Faute De L'Abbe Mouret, Le Petit Matin, Le Fou Du Labo, Julie La Rousse, and the French romantic melodrama Martin Roumagnac, which starred Marlene Dietrich. Lion and Dietrich sang a famous duet, "Wenn die beste Freundin mit der besten Freundin", a song which allegedly had lesbian overtones. It became a hit in Weimar Berlin prior to Dietrich's departure for Hollywood.