The Queen served her country for 70 years and passed away peacefully at her home, Balmoral Castle, in Scotland.
Buckingham Palace announced the news on Thursday afternoon: "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."
Her son, Charles, will now become King and he released a statement following the death of the Queen.
The King said: "The death of my beloved Mother, Her Majesty The Queen, is a moment of great sadness for me and all members of my family."
News of the queen's health emerged on Thursday when her doctors said she was under medical supervision, prompting her family to rush to be by her side at Balmoral.
Her last public engagement came only on Tuesday, when she appointed Liz Truss prime minister - her 15th and final PM.