It was the queen's first official public appearance since the country went into lockdown in late March.
Her "official" birthday - the anniversary of her coronation - in June would normally be marked with a large parade of soldiers through central London, known as Trooping the Colour.
But Buckingham Palace announced that the celebration would not go ahead in its traditional form due to restrictions on social gatherings in place to prevent the spread of coronavirus.
The event held in Windsor Castle was created by Garrison Sergeant Major Warrant Officer Class 1 Andrew Stokes and carried out by Major General Ghika, who commands the Household Division and all military support for London's civil response to coronavirus.
Queen Elizabeth, the world's oldest and longest reigning living monarch, has addressed Britain twice during the country's lockdown to galvanize the public. She has also taken part in her first video conference call to mark Carers Week with her daughter Anne, where she spoke to four carers who have the primary responsibility of looking after family members during the COVID-19 outbreak.
Prince Philip, the husband of Queen Elizabeth for more than seven decades, celebrated his 99th birthday on Wednesday, privately at Windsor Castle with muted celebrations due to the coronavirus crisis, as did the Queen when she celebrated her 94th birthday in April.
Elizabeth was born on April 21, 1926, in Bruton Street, central London and became queen in 1952 at the age of 25, meaning she has now reigned for more than 68 years.