[tjwmason]

Queen Mary II is reserved for the next Queen of England to be named Mary.

Queen Mary I reigned from 1553-1558. Then at the so called glorious revolution of 1688 Parliament declared William Prince of Orange and his wife Mary to be co-rulers, thus creating Queen Mary II (I am a Jacobite, and thus do not recognise this act or the reign of William and Mary). Thus the next Queen Mary will officially be called Queen Mary III; though that will not be for a while yet.

The ship the Queen Mary was not named for Mary Tudor, but rather for Queen Mary wife of one of the King Georges (I forget which one). Queens Consort (queens who are queens by virtue of being married to the king) do not have ordinal numbers applied to them, only Queens Regnant (those who are actual Sovereigns such as H.M. Queen Elizabeth II, Queen Victoria &c.). There have been very few Queens Regnant as the throne passes to the sons of the monarch in preference to daughters, thus the Sovereign has to have only daughters before a Queen Regnant comes along.

[bob3443]

Queen Mary was the name of Queen Elizabeth II's grandmother.
The QM2 is so named as the second ship by Cunard to bear the name Mary. This is also technically true for the QEII. However since there really is a Queen Eliz. II the QEII is meant to honor her. If another ship bearing Elizabeth's name it could be either QE2 or QEII2.