Hayden, the 2006 MotoGP world champion, had been hospitalized at the Maurizio Bufalini Hospital in Cesena, Italy, following the accident last week.
"It is with great sadness that Red Bull Honda World Superbike Team has to announce that Nicky Hayden has succumbed to injuries suffered during an incident while riding his bicycle last Wednesday,"
The statement also said that fiancée Jackie, mother Rose and brother Tommy, who flew in from the US, were at his side.
"On behalf of the whole Hayden family and Nicky's fiancée 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," 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."