Turner was the first female jockey to ride 100 winners in a year
Jockey Hayley Turner became the first female jockey to win a Group One race outright as she landed the July Cup at Newmarket on Dream Ahead.
Turner was drafted in after the colt's regular rider, William Buick, was required to ride at York.
She hit the front on David Simcock's 7-1 chance in the last 50 yards.
Alex Greaves was the only previous woman to win at the highest level - she dead-heated for first on Ya Malak in the Nunthorpe Stakes in 1997.
She was at Newmarket to see the latest landmark and hugged Turner in the winner's enclosure.
She's a fantastic rider but let's not forget the horse, either. Sebastian Vettel would not win the Monaco Grand Prix in a Mini
Dream Ahead's trainer David Simcock
Turner has reached several landmarks in her career, including becoming the first female jockey to ride 100 winners in a year .
She earned her first Group One success with a well-timed charge on Dream Ahead, who was last year's joint champion juvenile with Frankel and bounced back from coming fifth at Royal Ascot to finish ahead of Bated Breath and Hitchens.
"It's massive. I'm just thrilled. It's really fantastic," said Newmarket-based Turner, 28, who was born in Nottinghamshire.
"I haven't sat on the horse before so I can't take much credit. Obviously David has done a fantastic job and thanks to the owners for having me on board."
Simcock said William Buick, who was riding at York, and Jamie Spencer [in America] would normally have been the first two choices for the ride.
"Hayley has ridden winners for me and I was very confident. The majority of the time it's about the horse not about the jockey," he said.
DARLEY JULY CUP
1 Dream Ahead (H Turner) 7-1
2 Bated Breath (S Drowne) 9-1
3 Hitchens (S De Sousa) 28-1
Dist: ½, 1½
"She's a confident girl and deserved this."
Turner has been based with Newmarket trainer Michael Bell for a decade, and he told Racing UK: "From a very early age she always looked a special talent, she rides like a man.
"She's natural and very strong. Hayley has been the pathfinder, she has done it without family connections and has done it well."
Turner rounded off a memorable day by completing a Newmarket double with victory on 8-1 chance Overpowered in the penultimate race.
Earlier, jockey Barry McHugh's gamble paid off as he won the Bunbury Cup on Brae Hill (11-1) for Richard Fahey after going alone on the stands side.
At York, Green Destiny (6-1) landed the John Smith's Cup for William Haggas while 17-2 shot Tactician, owned by The Queen, won the John Smith's Silver Cup.
Jockey Eddie Ahern led from the front on Tactician for trainer Michael Bell.