The Duke of Edinburgh is retiring from royal duties this autumn, Buckingham Palace has announced.
The decision was made by Prince Philip himself and is supported by the Queen, a palace spokesman said.
The duke, who turns 96 next month, will attend previously scheduled engagements between now and August but will not accept new invitations.
The Queen “will continue to carry out a full programme of official engagements”, the palace said.
The duke carried out 110 days of engagements in 2016, making him the fifth busiest member of the royal family, according to Court Circular listings.
He is patron, president or a member of more than 780 organisations and will continue to be associated with them, but “will no longer play an active role by attending engagements”, Buckingham Palace said.
In the statement, the spokesman said the duke “may still choose to attend certain public events from time to time”.
BBC royal correspondent Nicholas Witchell said the duke “clearly feels he now wishes to curtail” his “familiar role” in support of his wife.
He added: “The Queen is going to continue, of that there is no doubt. She will continue, albeit with a somewhat lightened workload.”
He stressed there were “no health considerations” behind the move – other than the normal health precautions for a man in his mid-90s.
The duke attended Lord’s Cricket Ground to open a new stand on Wednesday and was heard joking at the event that he is the “world’s most experienced plaque unveiler”.
He is famed for off-the-cuff remarks he has made at royal engagements around the world over the years.
Prime Minister Theresa May said she offered the country’s “deepest gratitude and good wishes” to the duke following his announcement.
She added: “From his steadfast support for Her Majesty the Queen to his inspirational Duke of Edinburgh Awards and his patronage of hundreds of charities and good causes, his contribution to our United Kingdom, the Commonwealth and the wider world will be of huge benefit to us all for years to come.”
Labour leader Jeremy Corbyn wished the duke “all the best in his well-earned retirement”, saying: “He has dedicated his life to supporting the Queen and our country with a clear sense of public duty.
“His Duke of Edinburgh’s Award scheme has inspired young people for more than 60 years in over 140 nations.”
Prince Philip set up the awards in 1956 and they have become one of the UK’s best-known youth programmes, with young people carrying out challenges to earn bronze, silver or gold awards.
Liberal Democrat leader Tim Farron said: “Perhaps 30 years later than most people retire, the Duke of Edinburgh is announcing that that is what he is intending to do, and I think it is a moment to celebrate and take stock of the enormous achievements that he has made in his life so far.”
Scotland’s First Minister Nicola Sturgeon said the “steadfast support” the duke had given the Queen was “hugely admirable”.
“He has always served with enthusiasm and a healthy sense of humour,” she said. “I have always thoroughly enjoyed any time that I have spent in his company.”