Camilla, Duchess of Cornwall will be known as Queen Consort when Prince Charles becomes King.
Queen Elizabeth has confirmed her wish in a message marking the 70th anniversary of her reign.
The 95-year-old monarch said: "I would like to express my thanks to you all for your support.
"I remain eternally grateful for, and humbled by, the loyalty and affection that you continue to give me. And when, in the fullness of time, my son Charles becomes King, I know you will give him and his wife Camilla the same support that you have given me; and it is my sincere wish that, when that time comes, Camilla will be known as Queen Consort as she continues her own loyal service."
It's previously been suggested Camilla, 74 - who married Prince Charles in 2005 - may instead become Princess Consort.
At the time of their wedding, royal aides insisted Camilla didn't have any intention of becoming Queen and she was planning to become the first Princess Consort in British history.
But the Queen has now clarified that "when that time comes" she will be given the title of Queen Consort.
Meanwhile, the monarch is preparing to mark the day her father King George VI died and she acceded to the throne.
The Queen said: "As we mark this anniversary, it gives me pleasure to renew to you the pledge I gave in 1947 that my life will always be devoted to your service."
She also paid tribute to her late husband Prince Philip, who passed away in April at the age of 99.
The Queen wrote: "I am fortunate to have had the steadfast and loving support of my family. I was blessed that in Prince Philip I had a partner willing to carry out the role of consort and unselfishly make the sacrifices that go with it. It is a role I saw my own mother perform during my father's reign."
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