Admirals of Germany have existed since the founding of German sea forces, first with the Reichsflotte and then most predominantly that of the Prussian Navy. German admirals led the German Navy through World War I, as leaders of the Imperial German Navy, as well as through the inter-war years of the Reichsmarine.
The rank of Grossadmiral (Grand admiral) was introduced in 1905 as the naval equivalent to the five-star rank of the Generalfeldmarschall (general field marshal) OF-10 in Heer (en: Army). Hans von Koester was the first German flag officer to hold this rank. Wilhelm II. would wear the uniform of a Großadmiral on occasions. Since as Emperor he was Commander-in-Chief of the Navy and thus not subject to promotions.
The rank of admiral was the highest rank until the rank of Großadmiral was introduced in 1905. Prince Adalbert of Prussia was the first and only admiral of the Prussian Navy and later the Navy of the North German Confederation. The rank was not used in the Imperial German Navy until 1892. In the Reichsmarine Admiral was again the highest of three flag officer ranks. With the creation of the Kriegsmarine and the expansion of the fleet a new rank, Generaladmiral, was introduced in 1936, followed by the rank of Großadmiral in 1939. Thus the rank of admiral became the third-lowest, roughly equivalent of a general in the Heer or Luftwaffe. When the Bundeswehr was formed in 1955 Admiral became the highest rank again. The Volksmarine of the National People's Army of the German Democratic Republic used ranks similar to those in the Soviet Navy. While technically there was a rank of Flottenadmiral (Fleet Admiral), Admiral was the highest rank any naval officer achieved.
The rank of Flottillenadmiral (Rear Admiral, lower half) was newly established in 1955 as the naval equivalent to Brigadegeneral. The rank roughly corresponds to the position of Kommodore in earlier German naval forces.