Fleet captain

Naval officer ranks
Flag officers
Admiral of the fleet Grand admiral Admiral General admiral Vice admiral Squadron admiral Lieutenant admiral Rear admiral Admiral-superintendent Port admiral Counter admiral Divisional admiral Commodore Flotilla admiral Schout-bij-nacht
Senior officers
Captain Captain at sea Captain of sea and war Flag captain Fleet captain Post-captain Ship-of-the-line captain Commander Frigate captain Corvette captain
Junior officers
Captain lieutenant Lieutenant commander Lieutenant Ship-of-the-line lieutenant Frigate lieutenant Lieutenant junior-grade Sub-lieutenant Corvette lieutenant Ensign Midshipman

Fleet captain (US) is a historic military title that was bestowed upon a naval officer who served as chief of staff to a flag officer. In the UK, a captain of the fleet could be appointed to assist an admiral when the admiral had ten or more ships to command.