The image posted on the royal family's official social media accounts showed a smiling Camilla wearing a chic green jacket and patterned scarf.
The caption read: "Wishing the Duchess of Cornwall a very happy birthday today!" followed by a cake emoji, adding: "#HAPPYBIRTHDAYHRH. Swipe up to find out more about HRH's life and work."
WATCH: Prince Charles and Duchess Camilla's garden is another world
The couple also enjoyed a glamorous night out at the 'A Starry Night In The Nilgiri Hills' event hosted by the Elephant Family in partnership with the British Asian Trust on Wednesday.
Her Majesty shared this message for Camilla
The Duchesses could not contain their giggles as the Queen gamely cut a cake with a ceremonial sword as the royal ladies attended the Big Lunch at the Eden Project. When told by an aide that there was a conventional knife available, the monarch replied: "I know there is, this is more unusual."
The royal family at the G7 Summit in June
Camilla was born on 17 July 1947 to parents Major Bruce Shand and Rosalind Cubitt.
She married her first husband Andrew Parker Bowles in 1973, with whom she has two children, Tom Parker Bowles and Laura Lopes. The couple later divorced in 1995.
Camilla married Prince Charles in Windsor in April 2005 when she became the Duchess of Cornwall and the couple celebrated their 16th wedding anniversary earlier this year.
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