Flagship of the Navy?

Technically, the flagship is the ship used by the comanding officer of a group of naval ships.  For example, LT Bulkeley's 77' Elco PT boat was the "flagship" of PT Ron3 - since Bulkeley was the Ron3 CO.  

For military ships in harbor, one is designated as SOPA (Senior Officer Present Afloat).  SOPA is determined by the seniority of the Commanding Officers of the ships in port, based on their signal number.  SOPA flies the "starboard" (a green & white) pennant from the yardarm.

The "flag officers" of most navies are: Commodore (1 star); Rear Admiral (2 star); Vice Admiral (3 star); Admiral (4 star); Fleet Admiral (5 star).  Shortly after WWII, the USN, USCG, and USPHS changed their 1 star rank to Rear Admiral, Lower Half; 2 star became Rear Admiral, Upper Half. 

Commodore is still used in many navies to designate the officer in command of the flotilla or task force/group if they are not a flag officer.

In the old days of sail, the most senior admiral was usually on the largest and most powerful ship in the fleet, with lesser ranked admirals on smaller ship.  During the 20th century, most ships became large enough that they could accomdate the fleet commander and his staff.  During WWII most admirals preferred a faster ship (heavy cruiser) over the largest one (battleship).

There are many other reasons for an Admiral to break his flag on a ship, other than being in command of the fleet or task force.  The Admiral may be the District, Area, or Fleet Commander presiding over the change of command of a ship under his command.  The Admiral may be visiting the ship for some other reason, like an inspection or handing out medals to the crew.  When I was serving aboard USCGC VIGOROUS, we embarked the USCG Officer Ancient Marnier at the seabuoy off New London, CT.   The Ancient Mariner happened to be a 2 star Admiral, and he was retiring.  The transfer of the "Ancient Mariner" title was to be made to another USCG officer at the USCG Academy during the Admiral's retirement ceremony.  The USCG Ancient Mariner is a ceremonial title given to the officer and enlisted person with the earliest qualification date as a "Cutterman".

Another term to think about is "Queen of the Fleet".  The Queen of the Fleet usually the oldest ship still in active service; which generally rules out the USS CONSTITUTION or HMS VICTORY, as they are more of a museum ship.  In the USCG, the Queen of the Fleet has gold hull numbers, and is currently the USCGC ACUSHNET.

I suppose in a monarchy, if the monarch chooses to board a warship, then that ship would become the ceremonial flag ship of the navy.   

There is generally no real "flagship of the navy" in any respectable navy for the simple reason that no respectable navy would be so small in size and so limited in scope as for it to be practical to command it from a single floating battlefield command.

I was always under the impression that the Flagship was the ship the most senior officer was aboard or the "Highest Ranked" flag officer. So when this person transfered from one vessel to another the "Flag" was also transfered to that corresponding vessel.

It was not so much the vessel as it was who was aboard her..that determined that it was a "flagship".

Sure, and it isn't always what you might call the biggest-baddest thing afloat

At the time the USS Greenwich Bay (AVP-41) was the flagship of the US fleet in the Mediterranean

This is the USS Blue Ridge (LCC-19) the Flagship of the US Seventh Fleet (Pacific Fleet).   No big guns here - self protection only. 

Gone are the days when the Admiral of the Fleet leads his ships into battle at the head of the battleline.   Today's fleet flagship is all about command and control.  The admiral must be in contact with all elements of his (her) fleet - communications is the priority on the flagship of today.

Of course whatever ship the admiral breaks his flag on - is the flagship. 

The Bismarck was indeed the flagship of the two-ship fleet during her first (and only voyage).  Admiral Leutgens called the shots and was in overall command over both the Bismarck and the Priz Eugen.

The Constituion is indeed still afloat, and actually sails around from time to time.

My references show it was Flagship during the war with the Barbary Pirates, but thats about it.

I'm just wondering if there  is such a thing as a "Flagship of the Fleet" anymore.

Am I incorrect that During WWII the HMS Hood...and thereafter the King George V was the British Flagship?

Bismark as German Flagship?

Yamato as Japanese Flagship?

US  ???????

HMS Victory is the oldest commissioned warship in the world,dating from 1778. She still serves as Flagship of the Second Sea Lord/Commander in Chief Naval Home Command.

Even though she doubles today as a Museum ship, she is still very impressive, I believe your USS Constitution comes second to this holding a commission since 1797; whether she is classed as Flagship I don't know, but at least she's still afloat!