French runner Lazzat held off Satono Reve to deny Japan a first triumph at Royal Ascot.
James Doyle was victorious aboard the 9-2 winner, trained by Jerome Reynier.
The jockey and winning owners Wathnan Racing, who also had the third-placed horse Flora Of Bermuda, were celebrating a double on the day after the earlier victory of Humidity in the Chesham Stakes.
Favourite Satono Reve was bidding to become the first Japanese-trained winner at the meeting after 12 previous attempts but was beaten by half a length.
As Doyle celebrated after the line, Lazzat unshipped his jockey and ran loose around the Ascot track before being caught.
Rebel's Romance won the Hardwicke Stakes to give Godolphin trainer Charlie Appleby his first victory at Royal Ascot since 2022.
It was an eighth top-level Group One victory for the horse, ridden by William Buick.
"He was the horse we needed. I'm just glad to get one on the board in the end," said Appleby.
Appleby's 6-4 favourite Treanmor had earlier finished fifth behind winner Humidity in the Chesham Stakes and Rebel's Romance was his last Ascot runner of the week.
The globetrotting Rebel's Romance added Royal Ascot to an impressive CV which has brought big victories in the United States, Dubai and Hong Kong.
At seven years old, he is oldest winner of the race for more than a century and adds to career earnings of more than £10m.
"We had one shot, one roll of the the dice left and what a partner. He's a dream horse - I'm blessed," said Buick.
"We gel together - he's my best friend."
The 6-4 favourite finished clear of Al Riffa with third place going to Ghostwriter, who was bought by Kia Joorabchian's Amo Racing for £2m this week.
In a week when temperatures reached 30C, Humidity was an aptly named winner of the Chesham Stakes.
The 4-1 shot, under James Doyle for trainer Andrew Balding, provided a fourth winner of the week for owners Wathnan Racing.
A brother of 2022 victor Holloway Boy, Humidity was bought by the Emir of Qatar's Wathnan team following a winning Newbury debut in the Cheveley Park Stud colours.