Kate Middleton, 36, gained the title Duchess of Cambridge upon marrying Prince William, 35, who is also known as the Duke of Cambridge.
Her title may change if Charles becomes king, as William and Kate will take on his former title, which will make Kate ‘Her Royal Highness, the Princess of Wales’.
But to make matters more confusing, the Duchess has more than one name already.
Senior married members of the royal family also have regional titles, which at the moment includes Kate, Prince William and Prince Charles, 69.
When Kate and William married they were also given Scottish titles, reportedly to reflect the fact they met at St Andrews University.
Prince William was given the title Earl of Strathearn which makes Kate the Countess of Strathearn.
Prince Charles has the title Duke of Rothesay which is the historic title held by the heir to the Scottish throne before the two royal families merged in the early 1600s.
Kate and William also have a another name – in Northern Ireland they’re known as Baron and Lady Carrickfergus, another title they were gifted by the Queen on their wedding day.
So what do Kate and William refer to each other as?
In interviews, Prince William regularly refers to his wife as her full name, “Catherine”.
But reports have also revealed William has a nickname for Kate – he is regularly heard calling her “poppet” in public.
The public have coined their own nicknames for the Queen over the years – even her family have preferred names they would like to use.
While ‘Lizzy’ and ‘Liz’ may appear the most obvious choices, the nicknames family members, and even Prince Philip, have chosen to call are a little out of the ordinary.
Growing up the Queen’s childhood nickname was ‘Lilibet’, according to Now To Love.
The name is said to have come about after Her Majesty struggled to pronounce her own name.
But as she got older the nicknames did not disappear.
Prince Philip reportedly calls his wife ‘cabbage’ – information which emerged after the release of The Queen film, reported Sun Online.
What will Meghan Markle be called when she marries Prince Harry?