In a message marking the 70th anniversary of her reign, the Queen said it was her "sincere wish" that Camilla would have that title.
There had been suggestions Camilla would be known as Princess Consort.
But the Queen's announcement paves the way for her to be known as Queen Camilla in the future.
A Clarence House spokesman said the Prince of Wales and Duchess of Cornwall were "touched and honoured".
The Queen's message, marking her accession to the throne in 1952, directly addresses the unresolved question of the Duchess of Cornwall's future title.
