The Royal Family has had a long association with Ascot.
The racecourse in Berkshire was founded by Queen Anne in 1711, and has since received the patronage of a further eleven monarchs.
The Ascot summer race meeting officially became a Royal week in 1911, during the reign of King George V.
The Queen, 93, has been attending the fixture since 1946, when she was then Princess Elizabeth.
Her Majesty is owner and breeder of many thoroughbred horses and shares her interest in horses with many members of her family.
Her own horses have won races at Royal Ascot a number of times, the first being in 1953.
What happens on the day?
Each day of the week begins with the Royal Procession at 2pm, when The Queen and accompanying members of the Royal Family arrive along the track in horse-drawn landaus.
King George IV started the traditional carriage procession at Royal Ascot in 1825.
The first race of the day begins at 2:30pm and the royals spend the rest of the afternoon watching from the Royal Enclosure.
Can you buy tickets for the Royal Enclosure?
Unfortunately not. It was first established in 1807 exclusively for the family, guests and household of King George III, and to this day membership continues to be by invitation-only.
Members can book badges for themselves and their guests, book car parking or sponsor new members.
What do the royals wear?
There is a strict dress code for the Royal Enclosure.
Ladies should wear dresses and skirts of modest length, which fall just above the knee or longer, while dresses and tops should have straps of one inch or greater.
While trouser suits and jumpsuits are welcome in the Royal Enclosure, strapless, off-the-shoulder, halter neck and spaghetti straps are not permitted. Jackets and pashminas may also be worn.
Hats are also a must or a headpiece which has a solid base of 4 inches (10cm) or more in diameter is acceptable as an alternative to a hat. Fascinators are not permitted.
Men are required to wear either black or grey morning dress, which must include a waistcoat and tie, a black or grey top hat and black shoes worn with socks.
The Queen attends with members of the Royal Family throughout the week, who join her in the carriage procession.
There have been several notable debuts at the racecourse.
Princess Diana attended for the first time in 1981, just weeks before her wedding to Prince Charles.
The Duchess of Cambridge made her debut in 2016 wearing a white lace Dolce & Gabbana dress.
The Duchess of Sussex channelled Audrey Hepburn in a white Givenchy shirt dress with a black waist belt last year.