Which is correct:
- Mary Queen of Scots birthplace
- Mary Queen of Scots' birthplace?
Which is correct:
If you wish to make a possessive of a longer title — grammatically a noun phrase consisting of a noun and an appositive — you may attach an ’s to the end of the phrase. Since Scots is plural, however, you only add an apostrophe:
Their demands were equally uncompromising, including the restoration of traditional Catholic worship, the trial of Cecil, the release of the Duke of Norfolk and the recognition of Mary, Queen of Scots’ title to the throne. — J. Derek Holmes, Bernard W. Bickers, A Short History of the Catholic Church, 1984, 158.
The comma after Mary really shouldn’t be there.
A surprising number of publications grammatically reduce Mary’s sovereignty to a single Scottish subject:
These allies lost and Mary Queen of Scot's future was apparently to be the daughter-in-law of Henry VIII. — Gerard Lacey, The Legacy of the DeLacy, Lacey, Lacy Family 1066–1994, 1994, 88.
Needless to say, this is the wrong way to form a possessive of Queen of Scots.
Whether Mary Queen of Scots’ birthplace or (the) birthplace of Mary Queen of Scots is a better stylistic choice depends on how you’re using it in a sentence. If it’s clear you’re only talking about the ill-fated queen, you’d probably be better off with Mary’s birthplace or some such.
Use "Mary Queen of Scots' [or Scots's] birthplace."
When a title is integral to the name, it still takes a possessive case. Hence:
Alexander the Great's horse
Catherine of Aragon's husband
The King of the Britons' [or Britons's] retinue
There's at least one example of a writer's guide from the early 20th century prescribing this usage for Mary Queen of Scots. This combination makes sense since in each of the cases the title (whether referring to a people or not) is a part of the identifying proper noun. (See rule 5 on compounds here.)
The concern you express in the comments is interesting. What if you need to distinguish the people (the Scots) from the title (Mary Queen of Scots)? First, I'd suggest this shakes out from usage and context: seldom would one say "Mary Queen," since "Queen" as a title by itself usually precedes the name, as in "Queen Mary" or "Queen Elizabeth." Second, if ambiguity were a worry, there is a great way to avoid the possessive case:
The birthplace of Mary Queen of Scots
Finally, I've been putting an alternative in brackets. Because the total name is a singular name, some style guides would insist that one use the singular possessive form ('s) rather than the plural ('). However, some guides allow for the use of (') alone when the singular name ends in "s." As someone who has an "s" name who vacillates back and forth between the usages, I leave that up to you.