The King has left hospital after undergoing treatment for an enlarged prostate.
The monarch, 75, smiled and waved to the public as he left the private London Clinic with the Queen by his side.
Buckingham Palace said in a statement that the King has "rescheduled forthcoming public engagements to allow for a period of private recuperation".
He will not carry out royal engagements for up to a month as he recovers from the surgery, Sky News understands.
The palace added that the senior royal thanked all involved in his hospital visit and treatment, and was "grateful for all the kind messages he has received in recent days".
The King was admitted to hospital on Friday morning as Camilla accompanied him.
The princess left earlier on Monday to recover at home in Windsor. It is understood the King visited her ahead of his own treatment.
The King arrived in London from Norfolk on Thursday afternoon ahead of the procedure after a couple of behind-the-scenes official duties.
He was diagnosed with the benign condition on 17 January after going for a check-up when he was experiencing symptoms.
It is understood the King shared details of his diagnosis to encourage other men who may be experiencing symptoms to get checked in line with public health advice.
NHS England said the "enlarged prostate" page on the NHS website received one visit every five seconds on the day the King's diagnosis was announced, with further huge boosts in visits in the following days.
What is an enlarged prostate?
The NHS describes a benign enlarged prostate as a condition that can affect how people urinate, and is common among men aged over 50.
"It's not a cancer and it's not usually a serious threat to health," the NHS said on its website.
"Many men worry that having an enlarged prostate means they have an increased risk of developing prostate cancer. This is not the case."
But benign prostate enlargement can sometimes lead to complications, such as a urinary tract infection, chronic urinary retention, and acute urinary retention.
The NHS also said the cause of prostate enlargement is unknown, but it is believed to be linked to hormonal changes as a man gets older.