Admiral of the Fleet is a supreme naval position that has existed both in historical navies and several modern day navies of the 21st century. The rank is typically held by the senior most Admiral of an entire naval service. Admiral of the Fleet can trace its origins to the Middle Ages, where the title was typically granted to a Lord or nobleman who was appointed by a monarch to raise and command a Navy for a specific campaign.

Admiral of the Navy is a similar title to Admiral of the Fleet and is generally considered senior. Some nations consider the rank of Admiral of the Fleet and Fleet Admiral to be synonymous.

The following are present and historical nations which have used the rank Admiral of the Fleet:

• United Kingdom (Admiral of the Fleet)
• Soviet Union (Admiral of the Fleet of the Soviet Union)