Often sided by her husband, Prince Charles, and one of her closest friends, the Duchess of York, Diana consistently attended the annual event, with small breaks to welcome her children Prince William and Prince Harry.
Scroll through the gallery – or click through, if you're on desktop – to see her best Royal Ascot looks through the years...
Photo: © Getty Images
1980
Then Lady Diana Spencer attended her first-ever Royal Ascot with her fiancé, Prince Charles, on June 16, 1980. She stunned in a purple-and-white checked dress, paired with lilac heels, a matching wide-brimmed hat and clutch, and white gloves.The royal couple went on to wed a month later on July 29 at St. Paul's Cathedral in London.
Photo: © Tim Graham Photo Library via Getty Images
Photo: © Tim Graham Photo Library via Getty Images
Photo: © Tim Graham Photo Library via Getty Images
1981
Her second year at the Royal Ascot saw a fiery red beginning! The princess wore a Bellville Sassoon outfit on June 3, 1981.She paired a red clutch and shoes with a matching hat, and her billowing red-and-white striped sleeves underneath a longline blazer and skirt made the outfit the perfect '80s look.
Photo: © Anwar Hussein/Getty Images
1985
This year marked Diana's first time back at the Ascot since welcoming her children, William and Harry, in 1982 and 1984, respectively.Diana made her return looking every inch a style star. Her pink outfit – crafted by designer Jan Van Velden – featured a pussy bow tie. She wore a wide-brimmed hat and beige shoes, too, carrying matching gloves in her hands.
Photo: © Tim Graham Photo Library via Getty Images
1986
Polka dots were the name of the game for Lady Diana this year! Joining Princess Anne and the Queen Mother, the Princess of Wales looked chic as ever in a white-and-black polka dot number, paired with a matching saucer hat and pumps.Photo: © Derek Hudson/Getty Images
1986
In the prime of 80s fashion, Diana was the picture of elegance in a white button-up peplum top, paired with a white pencil skirt, heels, her classic three-stand pearls and a Somerville hat to match.Photo: © Jayne Fincher/Getty Images
1987
What a stylish trio! Diana was joined by friends Sarah, Duchess of York, and Carolyn Cotterell, who were all decked out for the day.Diana looked beautiful in a floral skirt suit and white hat, while her close friend Sarah brought some sunshine in a similar skirt suit silhouette, only in yellow-and-white polkadots.
Photo: © Tim Graham Photo Library via Getty Images
Photo: © Tim Graham Photo Library via Getty Images
Photo: © Lucy Levenson/Getty Images
1988
The Princess of Wales went with a more low-key look than her usual, pairing a Catherine Walker coat and dress with a pale blue handbag, gloves and a white Philip Somerville hat.Perhaps Duchess Kate took after Diana's love for the British designer?
Photo: © Jayne Fincher/Getty Images
1990
The '90s were all about colour blocking, and the princess definitely got the memo.Diana paired a double-breasted purple-and-pink Catherine Walker skirt suit with purple pumps and a matching hat. Charles wore a grey morning suit and black top hat.
Photo: © Jayne Fincher/Princess Diana Archive/Getty Images
The Princess of Wales wore her red blazer with a purple skirt and yellow top, while the Duchess of York was dressed in a head-to-toe red ensemble.
Photo: © Jayne Fincher/Princess Diana Archive/Getty Images
1991
Sarah, Duchess of York, and Princess Diana decided to coordinate yet again as they both turned heads in pastels.Diana wore a beautiful yellow-and-white skirt suit, while Sarah stuck with a cream double-breasted number and large straw hat.
Photo: © Tim Graham Photo Library via Getty Images
1992
For her seemingly last appearance at the annual races, Diana wore a magenta dress and matching hat as she arrived alongside the Queen Mother.Photo: © Jayne Fincher/Hulton Archive/Getty Images