The 2006 MotoGP champion, Nicky Hayden has died from injuries sustained when he was hit by a car while cycling in Italy last Wednesday.
Hayden was riding near Rimini when the accident occurred.
He was subsequently rushed to a local hospital with severe head and chest trauma and several fractures, before being transferred to the Bufalini Hospital in Cesena.
The 35-year-old's condition was not stable enough to perform surgery to relieve the pressure on his skull caused by cerebral edema.
He remained in a critical condition in intensive care through the weekend.
A statement from the hospital said Hayden died on Monday.
"On behalf of the whole Hayden family and Nicky's fiance Jackie I would like to thank everyone for their messages of support - it has been a great comfort to us all knowing that Nicky has touched so many people's lives in such a positive way," his brother Tommy Hayden said.
"Although this is obviously a sad time, we would like everyone to remember Nicky at his happiest - riding a motorcycle.
"He dreamed as a kid of being a pro rider and not only achieved that but also managed to reach the pinnacle of his chosen sport in becoming world champion. We are all so proud of that.
"Apart from these 'public' memories, we will also have many great and happy memories of Nicky at home in Kentucky, in the heart of the family. We will all miss him terribly.
"It is also important for us to thank all the hospital staff for their incredible support - they have been very kind.
"With the further support of the authorities in the coming days we hope to have Nicky home soon."
Hayden made 217 MotoGP starts between 2003 and '16, beating Valentino Rossi to the 2006 world championship in the fourth of his six seasons with the factory Honda team.
He moved to Ducati in 2009 and spent his final two full-time seasons with the Aspar Honda team before switching to the World Superbike Championship with the Japanese firm last year.
The American made two more MotoGP starts in 2016, as an injury replacement for Marc VDS Honda's Jack Miller at Aragon and at Phillip Island for factory Honda rider Dani Pedrosa.
Hayden was 13th in the 2017 World SBK standings after five rounds, failing to finish the first race at Imola the weekend before his accident and crossing the line 12th in the other.