Siegfried Friedrich Heinrich Müller (26 October 1920 – 17 April 1983), referred to as "Congo Müller" (Kongo-Müller), was a German-born mercenary who served as an officer with 5 Commando during the Congo Crisis. A former officer-candidate in Nazi Germany's Wehrmacht who continued to wear his Iron Cross, Müller acquired particular notoriety in West and East Germany in the mid-1960s amid extensive press coverage of his involvement in war crimes in the Congo and overt nostalgia for the Nazi era. ()