The 36-year-old royal will most likely take on the title of Queen Catherine when she stands alongside her husband as he becomes King William.
“The wife of the king is by tradition a queen,” Royal historian Marlene Koenig, of the Royal Musings blog told Hello!. This is officially known as the Queen Consort.
An exception to this, however, is Camilla, who is married to Prince Charles. When Charles becomes King, Camilla will become Princess Consort.
However then if you’re wondering why Prince Phillip isn’t called King Phillip, Koenig explains that too.
“The husband of a queen, in most monarchies, has to be created a title,” she adds.
Fans of The Crown will remember this well.
Now should Kate go on to outlive her husband and Prince George becomes king, Kate will become known as the Queen Mother.
“When [Prince] George is King (if Catherine is still alive), she can choose to be styled as HM Queen Catherine, the Queen Mother,” says Koenig.
While Prince George will move up in line when Prince William becomes king, Princess Charlotte will too, but as the chances of her ever becoming monarch remain slim, her title will also eventually change.
Princess Charlotte will become the Princess Royal, however, she cannot take that title just yet as someone in the royal family already holds it.
Queen Elizabeth’s oldest daughter, Princess Anne, currently holds this title as it is bestowed on the eldest daughter of the monarch.
Unless something major happens - like Prince George abdicating the throne when his time comes (it's happened before), this is the title Princess Charlotte will likely hold for most of her life.