Queen Elizabeth II, the UK’s longest-serving monarch, has died at Balmoral aged 96, after reigning for 70 years.
Her family gathered at her Scottish estate after concerns grew about her health earlier on Thursday.
The Queen came to the throne in 1952 and witnessed enormous social change.
With her death, her eldest son Charles, the former Prince of Wales, will lead the country in mourning as the new King and head of state for 14 Commonwealth realms.
In a statement, Buckingham Palace said: “The Queen died peacefully at Balmoral this afternoon.
“The King and the Queen Consort will remain at Balmoral this evening and will return to London tomorrow.”
All the Queen’s children travelled to Balmoral, near Aberdeen, after doctors placed the Queen under medical supervision.
Her grandson, Prince William, is also there, with his brother, Prince Harry, on his way.
Obituary: A long life marked by a sense of duty
Queen Elizabeth II’s tenure as head of state spanned post-war austerity, the transition from empire to Commonwealth, the end of the Cold War and the UK’s entry into – and withdrawal from – the European Union.
Her reign spanned 15 prime ministers starting with Winston Churchill, born in 1874, and including Liz Truss, born 101 years later in 1975, and appointed by the Queen earlier this week.
She held weekly audiences with her prime minister throughout her reign.
The Queen was born Elizabeth Alexandra Mary Windsor, in Mayfair, London, on 21 April 1926.
The death of Queen Elizabeth II is a watershed moment for Britain, at once incomparable and incalculable.
It marks both the loss of a revered monarch — the only one most Britons have ever known — and the end of a figure who served as a living link to the glories of World War II Britain, presided over its fitful adjustment to a post-colonial, post-imperial era and saw it through its bitter divorce from the European Union.
There is no analogous public figure who will have been mourned as deeply in Britain — Winston Churchill might come closest — or whose death could provoke a greater reckoning with the identity and future of the country. Elizabeth’s extraordinary longevity lent her an air of permanence that makes her death, even at an advanced age, somehow shocking.
The ups and downs of the queen’s seven-decade reign were many, a tapestry of events that traces the history of the 20th and early 21st centuries. Britain and 15 other Commonwealth realms over which she presided are a shadow of the empire-in-decline she inherited in 1952. How many of those countries will continue to recognize the British monarch as their head of state is an open question.
The foibles of her family were endless and endlessly dissected — from the abdication of her uncle, Edward, to marry a divorced American woman, Wallis Simpson, which set in motion the events that put her on the throne, to the painful rupture between her grandson, Prince Harry, and the rest of the family after his marriage to Meghan Markle, an American actress.
The House of Windsor has weathered the upheavals thanks largely to the anchoring role the queen has played. With her dignity and sense of duty, she rose above the tabloid headlines, whether about her troubled sister Princess Margaret; her eldest son and heir, Prince Charles, and his ill-fated marriage to Diana, Princess of Wales; or her middle son, Prince Andrew, who is under legal scrutiny linked to his dealings with the disgraced financier Jeffrey Epstein.