The Duchess of Cornwall is to be honoured by the Queen for personal services to the crown.
The monarch has appointed Camilla to the highest female rank in the Royal Victorian Order, Buckingham Palace said on Monday.
The announcement that the Duchess has been made a Dame Grand Cross comes on the day of the seventh wedding anniversary of Camilla and Prince of Wales.
The royals wed on 9 April, 2005 in a civil ceremony at the Guildhall in Windsor after spending a number of years as a couple.
Once seen as the other woman in the marriage of the Prince and Princess of Wales she has become an integral member of the Royal Family since she married Charles.
Awards under the Royal Victorian Order are in the Queen's personal gift and are given by the head of state to people who have served her or the monarchy in a personal way, and are bestowed independently of 10 Downing Street.
The Order was founded in April 1896 by Queen Victoria as a way of rewarding personal service to her.
It is likely the award recognises the 64-year-old Duchess' hard work as a member of the monarchy during the past seven years.
When most women her age would be looking forward to a slower pace of life she has carried out hundreds of royal engagements during that period.
The duchess has also taken on a wide range of patronages and travelled extensively overseas with the prince on official visits.
A Buckingham Palace spokeswoman said Camilla will be invested with the insignia of her rank at a later date.
Camilla has been made a Dame Grand Cross, the highest female rank that the Monarch can give.
It comes on the day of her seventh wedding anniversary to Prince Charles.