"Today, I am proud to create him Prince of Wales" the king said on television during his first address to the nation.
He said William’s wife Kate was named Princess of Wales.
The sovereign said Prince William will also assume the Scottish titles including the Duke of Cornwall and the Duke of Rothesay.
Charles III said his wife becomes his Queen Consort.
"I count on the loving help of my darling wife, Camilla. In recognition of her own loyal public service since our marriage 17 years ago, she becomes my Queen Consort," he said.
Charles III mentioned his younger son Harry and the son’s wife Meghan Markle, a US national, who both permanently reside in the US.
"I want also to express my love for Harry and Meghan as they continue to build their lives overseas," the king said.
Prince Harry and Meghan stepped down as senior members of the royal family, effective from March 2020. The pair moved to the United States, bought a house on the Pacific coast in Santa Barbara (California), and are raising their son Archie and daughter Lilibet Diana.