The king, who became monarch last September, will outline Prime Minister Rishi Sunak's priorities for the year ahead, which will likely see a general election.
"I can confirm that the state opening of parliament will take place on 7 November 2023," said Mordaunt.
Charles deputised for his late mother Queen Elizabeth II at the opening of parliament in 2022, but it will be the first time he has delivered the set-piece speech since becoming king.