Royal Ascot is so-called because it dates back to 1711 when it was founded by Queen Anne.
Every year the five day racing event is attended by Queen Elizabeth II and other members of the British Royal Family, arriving each day in a horse-drawn carriage.
But the real spectacle of Royal Ascot, however, is arguably the fashion -- in particular the hats.
The wearing of hats is another tradition that traces its origins to the royals: it was not considered respectful to have one's head uncovered in the presence of the monarch.
On Ladies' Day, the hats often range from the exquisite to the eccentric. As one of the few remaining social occasions that requires ladies to wear hats, in recent years fashionistas have raised the bar with sculptural designs that are works of art in their own right.
This year's Royal Ascot takes place from Tuesday, June 14 to Saturday, June 18. Thursday, June 16, is Ladies Day.
Click through the slide show to see the best hats at Royal Ascot
Royals attending Day 1 included The Queen, who arrived in a carriage with her husband Prince Phillip. Her Majesty wore a bright yellow coat and hat decorated with a floral arrangement in shades of blue and tan.
Also arriving by carriage were Camilla, Duchess of Cornwall, who wore a large hat in a delicate shade of pink that matched her ensemble, and Princess Beatrice, the Queen's grand-daughter, who looked relatively subdued in navy.
Sophie, Countess of Wessex, who is the daughter-in-law of the Queen, was seen wearing a stylish cream-colored fit and-flare dress with balloon sleeves. She wore a matching wide-brimmed hat embellished with a tangle of feathers.
The Queen's daughter, Princess Anne was captured looking relaxed and happy. Like her sister-in-law Sophie, she was also wearing cream, this time a coat, with a constrasting black hat embellished with feathers.
Finally, Prince Harry cut a dash dressed in top hat and tails.
Click through the slideshow for photos of race-goers.