Fleet Admiral

Common military ranks in English
Navies	Armies	Air forces
Commissioned and Non-commissioned officers
Admiral of the fleet	Marshal or Field marshal	Marshal of the air force
Admiral	General	Air chief marshal
Vice admiral	Lieutenant general	Air marshal
Rear admiral	Major general	Air vice-marshal
Commodore	Brigadier or Brigadier general	Air commodore
Captain	Colonel	Group captain
Commander	Lieutenant colonel	Wing commander
Lieutenant commander	Major or Commandant	Squadron leader
Lieutenant	Captain	Flight lieutenant
Sub-lieutenant	Lieutenant or First lieutenant	Flying officer
Ensign	Second lieutenant	Pilot officer
Midshipman	Officer cadet	Flight cadet
Enlisted grades
Warrant officer or Chief petty officer	Warrant officer or Sergeant major	Warrant officer
Petty officer	Sergeant	Sergeant
Leading seaman	Corporal	Corporal
Seaman	Private	Aircraftman

An admiral of the fleet or fleet admiral (sometimes also known as admiral of the navy or grand admiral) is a military naval officer of the highest rank. In many nations the rank is reserved for wartime or ceremonial appointments. It is usually a rank above admiral (which is now usually the highest rank in peace-time for officers in active service), and is often held by the most senior admiral of an entire naval service.

It is also a generic term for a senior admiral in command of a large group of ships, comprising a fleet or, in some cases, a group of fleets. If actually a rank its name can vary depending on the country. In addition to 'fleet admiral' and 'admiral of the fleet', such rank names include 'admiral of the navy' and 'grand admiral'.

It ranks above vice admiral, rear admiral and usually full admiral, and is usually given to a senior admiral commanding multiple fleets as opposed to just one fleet. It is often classified in NATO nations as a five-star rank.

Admiral of the fleet is equivalent to an army field marshal. It is also equivalent to a marshal of the air force which in many countries has a similar rank insignia to admiral of the fleet.

The title admiral of the fleet can trace its origins to the Middle Ages, where the title was typically granted to a nobleman who was appointed by a monarch to raise and command a navy for a specific campaign.

The following articles contain specific information on the rank as it pertains to individual countries:

Ambiguity exists when translating the French amiral into English (into admiral of the fleet or admiral). A French title of amiral de la flotte, outranking a full admiral was invented in 1939 for Darlan, who was the only person in French history to hold that title.

...
Wikipedia