Princess Elizabeth Alexandra Mary was born in London on 21 April 1926.
At the time, no one expected her to be Queen as she was third in line to the throne behind her uncle and father.
During her record-breaking reign, she dedicated her life to serving her country and Commonwealth.
In a radio address in 1947 on her 21st birthday, she said: "I declare before you all that my whole life, whether it be long or short, shall be devoted to your service and the service of our great imperial family to which we all belong."
Princess Elizabeth became Queen in 1952 at the age of 25, when her father, King George VI, died.
The Queen's reign saw 15 different prime ministers, from Sir Winston Churchill to Liz Truss.
She was more widely travelled than any other international leader and the world's oldest head of state, always using her own distinctive form of quiet diplomacy to represent the United Kingdom around the world.
In 2015, she also became the longest-serving British monarch in history, passing the record set by her great-great-grandmother Queen Victoria.
As head of state and head of nation, Queen Elizabeth II was widely regarded as a symbol of stability, working tirelessly to make sure the monarchy remained relevant during a period of immense social, technological, and economic change.
She was a monarch without equal who will now be mourned across the globe.
