Henning Rudolf Adolf Karl von Holtzendorff was a German admiral during World War I, who became famous for his December 1916 memo about unrestricted submarine warfare against the United Kingdom. He was a recipient of Order of the Black Eagle and the Pour le Mérite with oak leaves and was one of just six Grand Admirals of the Imperial German Navy.

Submarine warfare is one of the four divisions of underwater warfare, the others being anti-submarine warfare, mine warfare and mine countermeasures.