Queen Elizabeth II has become the first British monarch to reach the milestone of 65 years on the throne.
Monday's Sapphire Jubilee is being marked with cannon salutes in London's Green Park and at the Tower of London.
Buckingham Palace also released a photo of the queen by David Bailey to mark the occasion. In the picture, taken in 2014, the monarch wears a suite of sapphire jewelry given to her by her father as a wedding gift in 1947.
The palace says the 90-year-old queen will spend the day quietly at her Sandringham estate in eastern England.
She became monarch on the death of her father, King George VI, from lung cancer at age 56 on Feb. 6, 1952.
Elizabeth surpassed Queen Victoria as Britain's longest-serving monarch in 2015.
The Associated Press