Archduchess Elisabeth Marie Henriette Stephanie Gisela of Austria (Hungarian: Erzsébet Mária Henrietta Stefánia Gizella; 2 September 1883 – 16 March 1963) was the only child of Rudolf, Crown Prince of Austria, and Princess Stéphanie of Belgium. Her father was the son and heir apparent of Emperor Franz Joseph I of Austria, and her mother was a daughter of King Leopold II of Belgium. She was known to her family as "Erzsi", a diminutive of her name Erzsébet in Hungarian. Later nicknamed The Red Archduchess, she was famous for becoming a socialist and a member of the Austrian Social Democratic Party. Source: Wikipedia (en)