Prince Philip trumped the record of 57 years and 70 days set by Queen Charlotte, the wife of King George III.
The 87-year-old, however, decided not to mark the milestone, letting friends and family know that he did not want a fuss made over the issue.
The Duke spent yesterday at home at Windsor Castle with his wife of more than 60 years, Queen Elizabeth, without any official engagements.
It has been more than 190 years since a royal consort has spent so long in the 'job'. Queen Charlotte died in 1818. Like Prince Philip, she was of German royal blood, a princess of Mecklenburg-Strelitz. She married George III in 1761.
Philip's duties as consort began on February 6, 1952, when his young wife, Princess Elizabeth, became Queen.
He is already the oldest serving partner of a reigning monarch. The Duke has also surpassed his own great-great-grandfather, Queen Victoria's partner Prince Albert, who is the second-longest-serving husband of a reigning monarch. Albert, however, acted as consort for 21 years before dying at just 42.
Unlike Albert, however, Philip does not hold the title of Prince Consort. Born Prince Philipos of Greece, Philip is a member of a German-Danish dynasty, the House of Schleswig-Holstein-Sonderburg-Glcksburg.
He renounced his foreign-sounding name, however, and took the name of his maternal grandparents, Mountbatten. It was not a name he could pass on. "I am the only the man in the country who can't give his name to his children," he reportedly complained.
Philip was made the Duke of Edinburgh, Earl of Merioneth and Baron Greenwich by King George VI shortly before his marriage to Princess Elizabeth in 1947. A decade later, the Queen made him a prince of the United Kingdom.
Since the Queen's accession, he has accompanied her on countless Commonwealth tours and state visits overseas, as well as on her public engagements all over the UK – by her side as her closest confidant.
In 2008, he undertook more than 350 engagements.
He is patron or president of some 800 organisations, with special interests in scientific and technological research and development, the encouragement of sport, the welfare of young people, conservation and the environment. The royal couple celebrated their 60th wedding anniversary in 2007.
Philip's decades of royal service form a stark contrast to his troubled early years. He was born on a kitchen table on the idyllic island of Corfu, the son of Prince Andrew of Greece, and with Danish, Greek, German and Russian ancestors. But Greece became a republic, his father drifted around Europe and his mother ended up in a lunatic asylum.
After being educated in Britain and Germany and then enlisting in the Royal Navy during the Second World War, Philip met a young princess. He could never have guessed she would become the Queen.