Britain's Prince William has been named the new Prince of Wales, while his wife Kate Middleton has become the Princess of Wales.
This follows the accession of William's father to King Charles III, after the death of Queen Elizabeth II.
It means Kate has become the first person since Diana, Princess of Wales to use the title - while William follows in his father's footsteps.
Diana held the title when she was married to Charles.
Britain's new Queen Consort, Camilla, was also technically the Princess of Wales when she married Charles in 2005, but never used the title.
In a televised speech on Friday, King Charles vowed to serve the people of the United Kingdom with "loyalty, respect, and love".
He also paid tribute to his mother for her "love, affection, guidance, understanding and example" in a speech from Buckingham Palace.
"Queen Elizabeth was a life well lived; a promise with destiny kept and she is mourned most deeply in her passing.
"That promise of lifelong service I renew to you all today," he said.
“Queen Elizabeth was a life well lived; a promise with destiny kept and she is mourned most deeply in her passing. That promise of lifelong service I renew to you all today.”
His Majesty The King addresses the Nation and the Commonwealth. pic.twitter.com/xQXVW5PPQ2
— The Royal Family (@RoyalFamily) September 9, 2022
He took the opportunity to pay tribute to his children.
On William, he said that "with Catherine beside him, our new Prince and Princess of Wales will, I know, continue to inspire and lead our national conversations, helping to bring the marginal to the centre ground where vital help can be given".
The couple's children are now Prince George, Princess Charlotte and Prince Louis of Wales.
As well as taking the Prince of Wales title, William has assumed his Scottish titles and succeeded him as the Duke of Cornwall.
Therefore, William and Kate are also the Duke and Duchess of Cornwall, and the Duke and Duchess of Rothesay in Scotland.
King Charles said: "I am proud to create him Prince of Wales, Tywysog Cymru, the country whose title I have been so greatly privileged to bear during so much of my life and duty."
He added: "I want also to express my love for Harry and Meghan as they continue to build their lives overseas."
A memorial service for Queen Elizabeth II was held earlier at St Paul's Cathedral in London, with 2,000 members of the public joining politicians.
Reporting by: IRN