Official Titles for Catherine Middleton, Wife of Prince William

Princess Kate? Duchess Catherine?

Press After Engagement Announcement
British Press Announces Engagement of William and Kate. Oli Scarff / Getty Images

What do we call her, the wife of Prince William?

The official title of the woman born as Catherine Elizabeth Middleton is Her Royal Highness The Duchess of Cambridge, according to the statement issued by Queen Elizabeth's press secretary in April of 2011 on the occasion of her marriage to Prince William. The Queen made William "Duke of Cambridge, Earl of Strathearn and Baron Carrickfergus," combining English, Scottish and Northern Irish titles.

With those titles, William is more formally known, according to protocol, as His Royal Highness Prince William, Duke of Cambridge -- the dukedom being the highest rank of the three new titles. So, on marriage, Catherine Middleton became the Duchess of Cambridge.  As well as, by William's titles, Countess of Strathearn and Baronness Carrickfergus.

She was not known as Kate, either, in her childhood, and she's still Catherine to many of her friends and family members.  "Kate" was a nickname that had stuck, though, by the time she went to college and met William.  She's called "Catherine" consistently by the royal family, including her husband in speeches.

Calling a woman "Princess So-and-So" is reserved for royal-born women, although when their first child's birth was registered, Catherine is recorded as Princess of the United Kingdom.

But what about Princess Diana? The quick answer is that while many referred to the wife of Charles, Prince of Wales, as Princess Diana (or even Princess Di), that title was not a correct usage according to protocol.

She was Her Royal Highness the Princess of Wales when married to Charles, Prince of Wales. After the divorce, the HRH or Her Royal Highness was taken away, but she was permitted to style herself "Diana, princess of Wales."

On this site, I use the common usage "Princess Diana" in many articles, because so many people who are looking for the information look for it under that title.

(Similarly, this site has used "women's suffrage" instead of "woman suffrage" even when it's anachronistic, because most people do their research looking for that rather than "woman suffrage.")

Camilla, second wife of Prince Charles, is (as of 2014) technically Princess of Wales, but she uses the title Duchess of Cornwall, based on one of Charles' many other titles, the Duke of Cornwall. Whether she will have the title of Queen if or when Charles succeeds his mother and becomes King is another matter entirely, a matter of some conflict -- but both Charles and Camilla are said to be leaning towards a "yes."

Meanwhile, just as Diana was generally called Princess Diana or Princess Di, it's likely inevitable that Catherine will be called Princess Catherine (I heard an interview the morning of the wedding with one of the royals calling her just that) or even Princess Kate.

One more thought. Catherine could one day become Queen Catherine, if or when William becomes King -- but many Queens Consort are known to history by their names before marriage.  

Thus, we remember Elizabeth Bowes-Lyon, Anne Hyde, Catherine of Valois,Eleanor of Aquitaine, and so on. So Catherine is likely to be known to history simply as Catherine Middleton.

Technically, those designated HRH Prince or Princess do not need surnames. William has used Wales in his military service.  If they do need a surname, it would be Mountbatten-Windsor, after Prince Philip's family name (adapted to make it less German sounding with World War II) and Elizabeth's family name.  The children of Catherine and William are likely to be known by the surname Cambridge during their childhood, until and unless William has become the Prince of Wales -- in which case, Catherine's title and styling will also change.

Some English Queens named Catherine:

And of course, there's Catherine the Great of Russia.