Breaking from her usual regal restraint, the monarch was caught up in the sheer delight of winning, cheering and clapping alongside her racing manager John Warren.
The heartfelt display not only defied her years, but also demonstrated just how intrinsically connected the Queen is to the equine world.
Fittingly, the monarch's historic win took part on Ladies Day at Royal Ascot. The Queen was joined by her granddaughters Princess Beatrice and Princess Eugenie, their father Prince Andrew, Princess Anne, her son Peter Phillips and his wife Autumn Kelly for day three of the racing action.
And it wasn't just the royal box celebrating as Ryan Moore drove her filly Estimate past the post. The 62,000-strong crowd showed their support for their beloved monarch, erupting with spontaneous applause as the cry 'Hats off for Her Majesty' echoed around the stands.
Traditionally, the Queen presents the Gold Cup to the winning owner, but this time it was finally her turn to collect the trophy.
The Duke of Edinburgh, who presented his wife with the Queen's Vase last year when Estimate won that race, was unable to share in her special moment as he recovers from recent stomach surgery.
So it fell to the couple's delighted son, Prince Andrew, to present his mother with her prize.
Sir Michael Stoute, trainer of Estimate, said of the momentous occasion, "It's a special thrill to win this race for The Queen, and it will have given her enormous pleasure — she really loves the game and it's a great recreation for her.
"She told me it was a very big thrill and thanked everybody involved… This win is very high on my list, because it's been done for a lady who, never mind being the Queen, loves racing, is a great supported of racing and is so good for British racing."