Royal lawyers working for the Duke and Duchess of Cambridge are going to court to try and stop any more private photos of Kate being published.
The pictures of Kate sunbathing without her bikini top on have been published in two European magazines and one foreign newspaper.
The lawyers will ask for the person who took the photos to be caught and charged, as well as getting the magazines who published them to be removed from shops.
The royal couple are said to be furious because the pics were taken without them knowing, while they were staying on a private holiday at William's cousin's house.
A spokesperson said: "It is unthinkable that anyone should take such photographs, let alone publish them."
St James's Palace confirmed on Friday afternoon that William and Kate would sue the magazine for what's called "breach of privacy", where they feel their privacy has been invaded.
Invasion of privacy
This latest situation has been compared to the intrusive behaviour of the press towards William's mother Diana, Princess of Wales, before her death.
A spokesman for the couple said last week that "a red line has been crossed", by the magazine publishing the pictures.
There are guidelines about what newspapers and magazines should and shouldn't publish.
One of these guidelines is that things that go on in private, should stay private, unless the press can prove that the public need to know what has happened.
Even if the photos are now removed, the incident raises big questions about the privacy of the royal family and how these pictures were taken in the first place.