"The Queen died peacefully at Balmoral this afternoon," Buckingham Palace said in a statement.
"The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow."
Her eldest son Charles, 73, automatically becomes king of the United Kingdom and the head of state of 14 other realms including Australia, Canada and New Zealand.
Her family had rushed to be by her side at her Scottish home, Balmoral Castle, after doctors expressed concern about her health. She had been suffering from what Buckingham Palace has called "episodic mobility problems" since the end of last year, forcing her to withdraw from nearly all her public engagements.
Queen Elizabeth II, who was also the world's oldest and longest-serving head of state, came to the throne following the death of her father King George VI on Feb. 6, 1952, when she was just 25.
She was crowned in June the following year.
