Willy Johannmeyer (sometimes mistakenly written Willi) was a German officer during World War II. He was also a recipient of the Knight's Cross of the Iron Cross with Oak Leaves, and, by the time of the dissolution of the Third Reich, the last Army adjutant (Heeresadjutant) to Adolf Hitler.

Willy Johannmeyer was born in Iserlohn, Westphalia, on 27 July 1915 After Adolf Hitler's rise to power in 1933, he joined the SS, becoming member Nr. 262992. In 1936, he assigned to the 64th Infantry Regiment as Cadet (Fahnenjunker) and two years later, he rose to the rank of Leutnant. By 1939, he was the leader of the Signal Corps training centre of the 503rd Infantry Regiment.

Johannmeyer took part in the invasion of France, having been appointed leader of the regiment's 2nd Company on 1 April 1940. In April 1941 he was transferred to the 14th Company of the regiment. Subjected to the Army Group North, the regiment fought mainly at the Leningrad front, after the invasion of the Soviet Union (Operation Barbarossa). Because of his excellent leading skills, he was soon appointed commander of the 2nd Battalion on 1 April 1942. There, for actions during the battles around the Lake Ilmen (May 1942), he was awarded Nazi Germany's second highest decoration, the Knight's Cross of the Iron Cross on 16 May 1942, soon followed by his promotion to Hauptmann (1 June 1942).