King Charles III will be the first reigning British monarch in over 30 years to take the salute from troops on horseback at the annual Trooping the Color.
The parade is a minutely choreographed military tradition dating back over two centuries, and was last ridden by the late Queen Elizabeth II in 1986 when she was 60.
Charles will ride at Horse Guards Parade, inspect soldiers on parade, and watch a ceremonial fly-past of aircraft from the palace balcony.
The parade starts at Buckingham Palace and moves down The Mall to Horse Guards Parade.
Prince William, his sister Princess Anne, and Charles will all ride at this year's event.
The late Queen Elizabeth II's Platinum Jubilee was celebrated with the parade last year, and it was one of her last public appearances before her death in September 2021 at the age of 96.
Charles's younger son Prince Harry and his wife Meghan kept a low profile at the event last year, but have not been invited this year.
The couple moved to the United States in 2020 and have reportedly criticized royal life.
The double birthday tradition was started by German-born King George II in 1748, who wanted to have a summer celebration as his own birthday was on October 30.