The Knight's Cross of the Iron Cross (German language: Ritterkreuz des Eisernen Kreuzes), or simply the Knight's Cross (Ritterkreuz) was a grade of the 1939 version of the Iron Cross (Eisernes Kreuz), which had been created in 1813. The Knight's Cross was the highest award made by Nazi Germany to recognise extreme battlefield bravery or outstanding military leadership during World War II. In the military orders of the Third Reich, it was second only to the Grand Cross of the Iron Cross (Großkreuz des Eisernen Kreuzes), an award that was given only once, to Nazi leader and Hitler's second-in-command Hermann Göring. He was granted it as a result of his services in building up the Luftwaffe (the German air force), and for serving as its commander-in-chief. The Knight's Cross was therefore functionally the highest order that German soldiers of all rank could obtain.
The Knight's Cross grade of the Iron Cross was worn at the neck and was slightly larger but similar in appearance to the 1813 Iron Cross. It was legally based on the 1 September 1939 renewal of the Iron Cross. The order could be presented to German soldiers of all ranks and to the allies of the Third Reich. Its first presentation was made on 30 September 1939, following the German Invasion of Poland, which marked the beginning of World War II in Europe. As the war progressed, some of the recipients distinguished themselves further, and a higher grade, the Oak Leaves to the Knight's Cross of the Iron Cross (Ritterkreuz des Eisernen Kreuzes mit Eichenlaub), was instituted in 1940. In 1941, two higher grades of the Knight's Cross with Oak Leaves were instituted. These were the Knight's Cross with Oak Leaves and Swords (Ritterkreuz des Eisernen Kreuzes mit Eichenlaub und Schwertern) and the Knight's Cross with Oak Leaves, Swords and Diamonds (Ritterkreuz des Eisernen Kreuzes mit Eichenlaub, Schwertern und Brillanten). At the end of 1944 the final grade, the Knight's Cross with Golden Oak Leaves, Swords and Diamonds (Ritterkreuz des Eisernen Kreuzes mit goldenem Eichenlaub, Schwertern und Brillanten), was created.
The last legal presentation of the Knight's Cross, in any of its grades, had to be made before 23:01 Central European Time 8 May 1945, the time when the German surrender became effective. A number of presentations were made after this date, the last on 17 June 1945. These late presentations are considered de facto but not de jure awards. In post-World War II Germany, the Federal Republic of Germany prohibited the wearing of Nazi insignia. In 1957 the German government authorized a replacement Knight's Cross of the Iron Cross, with an oak leaf cluster in place of the swastika, which could be worn by World War II Knight's Cross recipients. In 1986, the Association of Knight's Cross Recipients (AKCR) acknowledged 7,321 presentations made to the members of the three military branches of the Wehrmacht—the Heer (Army), Kriegsmarine (Navy) and Luftwaffe (Air Force)—as well as the Waffen-SS, the Reichsarbeitsdienst (RAD—Reich Labour Service) and the Volkssturm (German national militia). There were also 43 recipients in the military forces of allies of the Third Reich for a total of 7,364 recipients. Analysis of the German Federal Archives revealed evidence for 7,161 officially—de facto and de jure—bestowed recipients, including one additional presentation previously unidentified by the AKCR. The AKCR names 890 recipients of the Oak Leaves to the Knight's Cross, including the eight recipients who served in the military forces of allies of the Third Reich. The German Federal Archives do not substantiate 27 of these Oak Leaves recipients. The Swords to the Knight's Cross were awarded 160 times according to the AKCR, among them the posthumous presentation to the Japanese Admiral Isoroku Yamamoto, 13 of which cannot be supported by the German Federal Archives. The Diamonds to the Knight's Cross were awarded 27 times, all of which are verifiable in the German Federal Archives. The final grade, the Golden Oak Leaves to the Knight's Cross was verifiably awarded once to Hans-Ulrich Rudel on 29 December 1944.