The Duchess of Cambridge, Her Royal Highness, Countess of Strathearn and Lady Carrickfergus are just some of the many, many names and titles our future Queen is entitled to use whenever she fancies.
But those closest to her, including her husband, family and the royal family, simply call her either Catherine or Kate.
Over the years Kate has also had some unflattering nickname, most famously 'Waity Katie' during her long courtship with Prince William.
However her future husband's friends also gave her a cruel moniker, which mocked her mum Carole Middleton.
Early in their relationship, it's claimed some of William's circle called her "Doors to Manual" in reference to Carole's career as a flight attendant.
She worked for British Airways, which is where she met Kate's dad Michael, who was a flight dispatcher.
However after struggling to get decorations for Kate's fifth birthday party, Carole set up a delivery party supplies business - Party Pieces - which made her a millionaire.
An aide told the Sunday Times Magazine that Kate didn't like the nickname, but rose about it and didn't let it bother her.
They said: "It was never water off a duck's back, but she has extraordinary strength of character and resilience. I've never once seen or heard of her losing her temper."
Kate, who turns 40 today, also boasts some more affectionate and jokey nicknames from her family.
While Prince William refers to his wife as Catherine while on duty, apparently behind the scenes he called her Poppet.
But he's also jokingly said to call her DoD - short for Duchess of Dolittle.
But Kate gives as good as she gets, and has reportedly called her hubby "baldy".
This is a climb down from the more risqué "Big Willy" she reportedly used when they were first dating.
Nicknames are common in the royal family, with William known as Wombat and the Queen is Gary, from back when Wills and the rest of her grandchildren struggled to say Granny.
Meghan Markle calls Prince Harry Haz, and Prince Philip famously called his beloved wife Cabbage.
Speaking to The Sun, a royal insider said: "The royals are not very good at communicating with one another so this is one way around it. Nicknames are a way of taking the family tension out of things.
“They can also be a rather childlike family. They love to play games and they give each other silly presents. I think it's because they have to be so earnest in their public lives. Royals have always played in private.
"It's done with affection usually and there are grains of truth about what one feels about another."
