What you need to know:
- Kipyegon was victorious over the distance at the 2016 Rio Olympics, is current world silver medallist and is also in form this season, having clocked a best of 1:58.26 in the 800m at the Doha Diamond League meet.
- Also in the field in the third Diamond League of the season, just six weeks out from the Tokyo Games, will be the British pair of Laura Muir, the European champion, and Eilish McColghan.
Fresh from knocking more than 10 seconds off the women's 10,000m world record and then losing it two days later, Dutch runner Sifan Hassan will again show her versatility when she takes on Olympic champion Faith Kipyegon in the 1500m in the Florence Diamond League on Thursday.
The Ethiopian-born Hassan, who arrived in the Netherlands as a 15-year-old in 2008, claimed world titles in Doha in 2019 in both the 1500m and 10,000m.
Kipyegon was victorious over the distance at the 2016 Rio Olympics, is current world silver medallist and is also in form this season, having clocked a best of 1:58.26 in the 800m at the Doha Diamond League meet.
Also in the field in the third Diamond League of the season, just six weeks out from the Tokyo Games, will be the British pair of Laura Muir, the European champion, and Eilish McColghan.
"I'm not surprised, and I'm actually happy about it because I want to make the distance more exciting!" Hassan said of losing her 10,000m world record, set in Hengelo on Sunday, to compatriot Letesenbet Gidey at the Ethiopian trials at the same Hengelo track on Tuesday.
Another Briton honing her form, with just four more meets (Oslo, Stockholm, Monaco, Gateshead) to go before the July 23-August 8 Tokyo Olympics, is sprinter Dina Asher-Smith.
The reigning world 200m champion and 100m silver medallist will race over the longer distance in Florence, where the meet was moved to avoid the opening of Euro 2020 in Rome.
Asher-Smith is fresh from setting an Olympic-qualifying 10.92sec over 100m at Hengelo. She will be up against former two-time world champion Dafne Schippers of the Netherlands, Ivory Coast's experienced Marie-Josee Ta Lou, 100m bronze medallist at the Doha worlds, and world 200m bronze medallist Mujinga Kambundji from Switzerland.
Cheptegei in loaded field
Another middle distance maestro, Ugandan Joshua Cheptegei, who set new bests in the men's 5,000m in Monaco, 10,000m in Valencia and 5km road, also in Monaco, last season will kick off his Diamond League season over 5,000m.
The world 10,000m champion faces tough competition.
In-form Norwegian prodigy Jakob Ingebrigtsen will also be seeking to land his first 5,000m win of the season after victory in the 1500m in Gateshead.
There is also a trio of Ethiopians lying in wait: Selemon Barega and Hagos Gebrhiwet, who are ranked fifth and sixth respectively in the all-time list with 12:43.02 and 12:45.82; and Muktar Edris, reigning world 5,000m champion.
Moroccan-born Spaniard Mohamed Katir, who won the 5,000m with a personal best in Gateshead, will also be on the startlist.
In field events, local favourite Gianmarco Tamberi takes on a stellar field in the men's high jump, including Qatar's two-time defending world champion Mutaz Essa Barshim, Ukraine's Andriy Protsenko and Russia's world bronze medallist Ilya Ivanyuk.
Jamaica's Olympic 110m hurdles champion Omar McLeod looks in fine form after running the second-fastest time this year with 13.08 in Hengelo, while up-and-coming Dutchwoman Femke Bol goes in the women's 400m hurdles.
In the women's pole vault reigning Olympic champion Ekaterini Stefanidi of Greece will face Russia's world champion Anzhelika Sidorova and Briton Holly Bradshaw.