The 75-year-old monarch took a step back from his public duties after being diagnosed with an undisclosed form of cancer earlier this year and he's shelved all his engagements while he undergoes treatment - but a new report suggests he wants to return to the spotlight to attend his official birthday celebrations in London in June.
A source told the Daily Mail newspaper: "There are a number of key events His Majesty would love to attend coming up in the diary and this [the Trooping of the Colour] is at the top of the list."
The Trooping of the Colour is a ceremonial event held annually to celebrate the monarch's birthday. It's also known as the Sovereign's Birthday Parade and takes place in London with the monarch joining a procession of around 1,200 soldiers and musicians and more than 200 horses.
It also involves a fly-past and an appearance by the monarch on the Buckingham Palace balcony.
The Daily Mail's report suggests King Charles had been keen to ride his horse Noble - a gift from the Royal Canadian Mounted Police - during the event on June 15 but he may have to watch from a carriage or a podium instead.
The publication suggests a firm decision on whether the King will be able to attend has not been made yet and it will depend on the advice from his doctors.
The King's team is said to be planning various options that would allow him to attend but only if he "gets the nod" from medics.
It's also not yet clear whether Catherine, Princess of Wales will be able to attend the event after she also stepped away from royal duties following abdominal surgery in January.
She's expected to return to public life after Easter.