Vice-Admiral Sir Peter Grenville Lyon Cazalet KBE CB DSO DSC (29 July 1899 – 17 February 1982) was a senior Royal Navy officer who commanded the Reserve Fleet.

[1] He also served in World War II and was awarded the Distinguished Service Cross in July 1940.

[2] He became Commanding Officer of the cruiser HMS Durban in the Eastern Fleet in 1941 and saw action during the fall of Singapore.

[1] He became deputy director of Plans at the Admiralty in 1946, Commanding Officer of the cruiser HMS London in 1949 and Commodore at the Royal Naval Barracks Chatham in 1949.

[1] He went on to be Chief of Staff to the Flag Officer, Central Europe in 1950, Allied Chief of Staff to the Commander-in-Chief, Mediterranean Fleet in 1953 and Flag Officer commanding the Reserve Fleet in 1955 before retiring in 1957.