Queen Elizabeth has awarded the George Cross to all NHS staff across the UK.
The 95-year-old monarch praised the health service's workers for their "courage, compassion and dedication" over the past 73 years, and their response to the coronavirus pandemic.
In a handwritten message, on Windsor Castle-headed note paper, she wrote: "It is with great pleasure, on behalf of a grateful nation, that I award the George Cross to the National Health Services of the United Kingdom.
"This award recognises all NHS staff, past and present, across all disciplines and all four nations.
"Over more than seven decades, and especially in recent times, you have supported the people of our country with courage, compassion and dedication, demonstrating the highest standards of public service.
"You have our enduring thanks and heartfelt appreciation."
The George Cross was created by the queen's father, King George VI, in 1940 during the height of the Blitz in World War Two.
It is awarded for "acts of the greatest heroism or of the most courage in circumstances of extreme danger".
Health Secretary Sajid Javid praised the NHS's "incredible" work amid the coronavirus pandemic.
He said: "Those working in the NHS have done an incredible job caring for so many during this awful pandemic.
"The George Cross is the highest possible honour a civilian can achieve and I want to pay tribute to everyone across the NHS for their heroism and sacrifice."
NHS chief executive Sir Simon Stevens said: "This unprecedented award rightly recognises the skill and compassion and the fortitude of staff right across the National Health Service - the nurses, the paramedics, the doctors, the cleaners, the therapists, the entire team - who under the most demanding of circumstances have responded to the worst pandemic in a century and the greatest challenge this country has faced since the Second World War.
"Out of those dark times have come the best of what it means to be a carer and a health professional.
"In the face of adversity we have seen extraordinary team work, not just across the NHS but involving hundreds of thousands of volunteers, millions of carers, key workers and the British public who have played an indispensable role in helping the health service to look after many hundreds of thousands of seriously ill patients with coronavirus.
"And so, as we congratulate staff across the health service on this award, we recognise that completing the NHS COVID vaccination programme which is in the final stages is now the surest way out of this pandemic and provides a sense of hope."
The Duke and Duchess of Cambridge will celebrate the NHS's 73rd anniversary on Monday (05.07.21) by holding a service at London's St Paul's Cathedral.
Later in the day, they will host a Big Tea at Buckingham Palace's gardens, where they will be able to meet and thank some of the NHS staff, including respiratory ward nurses, counsellors and care workers.