Tributes have poured in for the young rider, who was the son of former motocross rider Phillipe Dupasquier.
This is everything you need to know.
Who was Jason Dupasquier?
Born 7 September 2001, in Bulle, Switzerland, Dupasquier is the son of former motocross rider Phillipe Dupasquier. He started his career in Supermoto and was a multiple time Swiss national champion.
Dupasquier then switched to circuit racing, and claimed the ADAC NEC Championship Moto3 crown in 2016, before moving onto the Junior world championship for 2017.
The teenager made steady progress throughout 2017, and was due to make his debut in the Red Bull Rookies Cup in 2018 when he broke his left femur in the second round of the Junior world championship.
Forced to sit out of the entire 2018 Rookies Cup campaign, Dupasquier returned in 2019 to finish eight overall, with a best result of fourth in Jerez.
Dupasquier made his Moto3 world championship debut last year, in 2020, and was riding again for the PrüstelGP squad in 2021.
He was in his second season in the MotoGP’s lightweight class, and was in the top 10 in the overall standings heading into the weekend.
Following a multi-rider accident on Saturday (29 May), during the qualifying session at the Italian Grand Prix at the Mugello circuit, Dupasquier was treated on the scene before being transported to Careggi Hospital in Florence.
The crash involved fellow riders Ayumu Sasaki and Jeremy Alcoba.
On Sunday (30 May), MotoGP said in a statement: “Following a serious incident in the Moto3 qualifying two session at the Gran Premio d’Italia Oakley, it is with great sadness that we report the passing of Moto3 rider Jason Dupasquier.
“Dupasquier was involved in a multi-rider incident between turns nine and 10, with the session red-flagged thereafter.
“FIM medical intervention vehicles arrived at the site immediately after and the Swiss rider was attended to on track before being transferred by medical helicopter, in a stable state, to Careggi Hospital in Florence.
“Despite the best efforts of circuit medical staff and all those subsequently attending to the Swiss rider, the hospital has announced that Dupasquier has sadly succumbed to his injuries.”
What tributes have been paid to him?
As news of the young rider's death circulated, many from the world of motorsport responded online with their condolences.
His team, Prüstel GP, said on Facebook, "We're devastated, and at this time all of our thoughts are with Jason's family. You'll be sorely missed and never forgotten, Jason."
The official Formula One account Tweeted: “No words can ever describe the pain of such a loss. Our thoughts are with Jason’s family, friends and the entire MotoGP community.”
British F1 driver George Russell wrote: “Motorsport can be so cruel. Thinkin of the family and friends of Jason Dupasquier and everyone in the MotoGP paddock. Ride in peace, Jason.”
Three time MotoGP champion, Jorge Lorenzo, wrote: “My deepest condolences to Jason Dupasquier’s family, friends and team.”
Ahead of Sunday’s 23 lap race, MotoGP grid staged a one minute silence in honour of Dupasquier. While Sunday’s races went ahead as planned, Dupasquier’s fellow Swiss racer Tom Luthi chose not to take part.
The race was won by world championship leader Fabio Quartararo, who, following his victory, waved a Swiss flag on the podium in Dupasquire’s honour.
Quartararo said: “It was tough because when you do the one minute silence, the emotion is coming really quick and it is difficult to stay focused.
“We got the win and that one was for Jason and his family.”
After winning his second World Superbike race in Portugal, six time champion Jonathan Rea also dedicated his victories to Dupasquier.
He said: “It’s been a great weekend for me, but there’s a real sour taste in my mouth after the news earlier about Jason.
“It’s terrible. I want to dedicate that to him and his family. I hope it gives them strength at this time.”