The world and Olympic champion delivered a thrilling finale to the third leg of the Wanda Diamond League with a bravura performance in a city that last saw a world record when World Athletics President Sebastian Coe broke the 800m mark here in 1981.
The pacemakers had been asked to take the field through in 3:54 pace, which seemed ambitious on a damp track after early rain. But that pace merely left Kipyegon full of running when she took the lead in the penultimate lap, as she blazed through the final 600m at unprecedented speed.
Her feet barely seemed to touch the track as she flew home in incomparable style to take down the eight-year-old standard of 3:50.07, set by Ethiopia’s Genzeba Dibaba in Monaco in 2015.
Kipyegon came agonisingly close to breaking this record at the Herculis meet in Monaco last year when she set her previous best of 3:50.37, and that seemed only to spur her on to make certain of the mark this season.
Having won both Olympic and world titles, the 29-year-old Kenyan was determined to claim the last great 1500m prize available with the world record.
"I said yesterday that I wanted to run a beautiful race, run my race, and see what is possible, and this was possible," she said.
"There’s still more to come. I’m still working on running faster than that, faster than 3:49. I’m really thankful today that I managed to run 3:49 and I’m still heading towards beautiful races in the rest of the season."
Kipyegon will now turn her attention to the 5000m in Paris next week before returning to Kenya to top up her training for another tilt at the record at the Herculis meeting in Monaco in July.
Such was her dominance tonight that world silver medallist Laura Muir finished almost eight seconds behind (3:57.09), while third-placed Jessica Hull (3:57.29) set an Australian and Oceania record.
The elite field of female middle-distance runners was overjoyed for Kipyegon, enveloping her in a group hug soon after the race to celebrate her achievement.
"We have really come along as 1500 women," Kipyegon said. “They are really special. We come along together, cheer one another. This is sport, we have to love each other and celebrate one another at our lowest moments and highest moments, and I really thank the ladies for coming along and running together and celebrating this world record together. We were part of this together."
It takes a lot to upstage the fastest man in the world, but Kipyegon managed it tonight.
However, world champion Fred Kerley was well satisfied with his work after he separated himself from the rest of the world’s best sprinters to win the 100m commandingly on a damp night in Florence.
Despite the cool conditions, Kerley triumphed over a world final quality field by a metre. He was the only man to dip under 10 seconds, clocking 9.94 to win from African record-holder Ferdinand Omanyala (10.05) and world bronze medallist Trayvon Bromell (10.09).
Earlier, Marie-Josee Ta Lou claimed the women’s 100m title in 10.97, in the absence of Briton Dina Asher-Smith, who withdrew from the race after cramping in her calf during warm up.
It may not have been a night for fast times over 100m, but it was perfect for the distance runners as world leads in both the men’s 5000m and women’s 3000m steeplechase proved.
Spain’s Mohamed Katir upstaged a star-studded 5000m field, defeating Yomif Kejelcha in a sprint to the death, to win by 0.03 in 12:52.09.
Third-placed Luis Grijalva of Guatemala set a national record of 12:52.97, just ahead of Olympic champion Joshua Cheptegei (12:53.81). The Ugandan champion was satisfied with his return to the track after almost 12 months, during which he had to overcome a career-threatening knee injury.
In the women’s steeplechase, it was Ethiopia’s Sembo Almayew who set a new standard for the season, running away from a high-class field to win in 9:00.71 from world U20 champion Jackline Chepkoech of Kenya (9:02.43) and fellow Ethiopian Zerfe Wondemagegn (9:04.61).
The fourth world lead of the night came in the women’s 400m hurdles, where Dutchwoman Femke Bol used her ambitious new stride pattern to great effect, setting a meeting record of 52.43 to win by almost a second from USA's Shamier Little (53.38).
"This was my first Diamond League race for this year and it is a great result, it met all my expectations," Bol said, adding that she is aiming for the gold medal at the World Championships in Budapest. “I am really, really happy. I executed the race like I wanted. I am looking forward to running in Hengelo in two days because there will be a lot of people from home. And, running the (flat) 400m gives me a different stimulus."
US heptathlete Anna Hall, underlining her credentials as one of the world’s most versatile athletes, set a personal best of 54.42 in third, less than a week after winning the heptathlon at the Hypo Meeting in Gotzis with the fifth biggest score in history.
World champion sprint hurdler Grant Holloway was back on top of his game in the 110m hurdles, defying the conditions to win in a sharp 13.05 from Switzerland’s Jason Joseph in a personal best of 13.10. Hurdler turned NFL star Devon Allen improved to finish third in a promising 13.19 after returning to track training after this year’s Super Bowl.
The brilliant teenaged Erriyon Knighton blasted through his first 200m of the year in an impressive opener of 19.89, the third-fastest time in the world this year. The US sprinter won handsomely, some three metres clear of the experienced Jereem Richards (20.28) and Aaron Brown (20.31) to make an early season statement.
"Now, I am very satisfied with this time - under 20 in the first race of the season," Knighton said.
The jumps were more affected by the slippery conditions underfoot but world silver medallist Woo Sanghyeok and rising US star JuVaughn Harrison staged a thrilling duel in the men’s high jump. Harrison took the win with a third-attempt clearance of 2.32m.
World champion Katie Moon’s second attempt clearance of 4.71m was good enough to deny Slovenia’s Tina Sutej victory, after she cleared the same height at the third attempt.
Italian athletes also stood tall in their home Diamond League meeting, claiming the women’s long jump, men’s triple jump and men’s shot put.
European indoor medallist Larissa Iapichino claimed her biggest victory over a world-class field in the long jump, leaping 6.79m to deny US jumper Tara Davis-Woodhall (6.74m) and Ukraine’s Maryna Bekh-Romanchuk (6.59m).
Cuban-born Andy Diaz Hernandez, who hopes to represent his adopted home of Italy at the World Athletics Championships this year, needed just one attempt to claim victory in the triple jump, setting a personal best of 17.75m, which bettered the Italian record.
Perennial contender Hugues Fabrice Zango was just seven centimetres behind (17.68m) in second.
Shot putter Leonardo Fabbri added to the Italian celebrations by winning a closely-fought competition with a season’s best throw of 21.73m, to pip 2017 world champion Tom Walsh of New Zealand (21.69m) and Czech thrower Tomas Stanek (21.64)
Olympic champion Valarie Allman won a dramatic women’s discus showdown with her fifth throw (65.96m) after world champion Bin Feng (65.50m) had led for much of the competition.
"Today was all about competing," Allman said. "The rain messed with my timing and my technique, I was not able to throw properly, but in the end I managed."
Appropriately for Italy’s premier one-day meeting, she planned to celebrate with "spaghetti and gelato".
Nicole Jeffery for World Athletics
*Subject to the usual ratification procedure
