Spectacular outfits will be on display as thousands of racegoers descend on Royal Ascot for Ladies' Day.
The Queen will join the glamorous guests at the world-famous racecourse where the oldest and most prestigious race, which runs today, has been renamed in the monarch's honour.
It will be known as the Gold Cup In Honour Of The Queen's 90th Birthday this year to commemorate her milestone.
One of her horses, Estimate, won the Gold Cup on Ladies' Day in 2013.
The Queen will no doubt be hoping for a change of luck when her horse, Guy Fawkes, runs in the King George V Handicap. Despite having three horses racing on Wednesday, the Queen failed to secure any wins.
Diploma, ridden by jockey Ryan Moore, came fifth in the last race of the day, while Make Fast with jockey David Probert finished seventh.
Rain has caused havoc for fashionable racegoers this week but has not impacted the racing, although more wet weather is expected.
The ground remained soft at the close of play on Wednesday but the clerk of the course said he was "pleased" with how the track had taken the rain.
Chris Stickels said: "The ground is not as bad as I thought it might be."
Rain is forecast this afternoon in Ascot with cloudy skies during the day.
Bookmakers William Hill is predicting, for the third day in a row, that the Queen opts for a blue hat and is offering odds of 3-1.
"Blue surely has to feature on Ladies' Day? It's not been a lucky colour for favourite backers so far though," William Hill spokesman Jon Ivan-Duke said.
The Queen wore a cyclamen pink outfit by Stewart Parvin with a hat by Angela Kelly for Wednesday's racing where she was joined by the Duke and Duchess of Cambridge for the first time.
Crowds cheered as Kate, who wore a beige Dolce and Gabbana dress and Jane Taylor hat, arrived in the parade ring.
The annual racing event has become a key date in the racing and social calendar, and Ladies' Day is one of the most popular for enthusiastic racegoers.
It is the third day of racing at the annual meet where more than 300,000 people are expected this week.