Camilla is now a Royal Knight of the Order of the Thistle, joining other members of the monarchy with the same honour like the Princess Royal and the Prince of Wales.
The announcement comes ahead of Charles spending his first official period in Scotland as head of state, known as Holyrood Week.
Buckingham Palace said in a statement: “The King has been graciously pleased to appoint the Queen to the Most Ancient and Most Noble Order of the Thistle.
“The Most Ancient and Most Noble Order of the Thistle represents the highest honour in Scotland. Revived by King James VII, the Order has a complement of 16 Knights (KT).”
The King is the sovereign of the order and appointments are his personal gift made independently of Downing Street.
Those made Thistle Knights have been recognised for holding public office or contributing significantly to national life.
The Queen was appointed chancellor of the University of Aberdeen in 2013 and in a speech to mark the 10th anniversary of her role at the institution, she said: “Coming to this university, and to this city, has always felt a bit like coming home to me.
“Firstly because my father’s family came from this part of Scotland, secondly because my husband and I are lucky enough to spend precious time each year in Aberdeenshire, and finally because 10 years ago, I received the great honour of being installed as chancellor of this very special university.”
Camilla is patron of Maggie’s Cancer Care Centres, founded in Edinburgh in 1996 and now with sites across Scotland, England and Wales.
She is also patron or president of a number of charities based in Scotland, including Crathie Opportunity Holidays, Scotland’s Gardens Scheme and Horseback UK, and is an honorary member of the local Ballater Women’s Institute and the Upper Deeside Art Society.