- King Charles III gave his first speech as monarch on Friday.
- He announced William will be the Prince of Wales and Kate Middleton will be the Princess of Wales.
William and Kate Middleton are officially the Prince and Princess of Wales, King Charles III announced in his first address to the UK as a monarch.
Charles became king on Thursday the moment his mother, Queen Elizabeth II, died. Buckingham Palace said she died peacefully at Balmoral Castle in Scotland.
The king gave his first address as monarch in a prerecorded speech that aired Friday.
In the speech, he spoke of his mother's legacy and the future of the monarchy, including the roles Prince William and Kate Middleton will play.
"Today, I am proud to create him Prince of Wales," the king said of the heir to the throne during the speech. "The country whose title I have been so greatly privileged to bear, during so much of my life."
Charles III added that William "assumes the Scottish titles which have meant so much to me."
The king then announced the Duchess of Cornwall and Cambridge will become the Princess of Wales.
"With Catherine beside him, our new Prince and Princess of Wales will, I know, continue to inspire and lead our national conservations, helping to bring the marginal to the center ground, where vital help can be given," the king went on to say.
William and Kate's Instagram handle changed to The Prince and Princess of Wales following the speech.
Kate assumes the role that Diana, William's mother, held before her 1997 death.
As Insider previously reported, the title was so closely connected to Diana that Camilla did not assume "Princess of Wales" when she married the king in 2005, going by the Duchess of Cornwall instead.
Camilla will now be known as the queen consort, according to the wishes of Queen Elizabeth.
It had not yet been announced if any other members of the royal family's titles would shift, though it's possible Prince Harry and Meghan Markle's children, Archie and Lilibet, may use HRH titles moving forward.