Jamie Hamilton's injuries have been described as "serious, but not life-threatening," after he crashed at high-speed during the Senior TT.
The Isle of Man event's main and final race was red-flagged after the incident on the Cronk-y-Voddy straight at the 11th Milestone on the second lap.
Clerk of the Course Gary Thompson said he was taken to hospital by air ambulance where he is being treated.
The 24-year-old crashed at one of the fastest parts of the 37-mile course.
The race was later re-started and John McGuinness won the shortened four-lap race.
One eye witness said the 24-year-old's bike "disintegrated in a big fireball".
Mark Dawson, who was watching from the area, added: "It was a massive tank slapper. He hit the tree on the far side."
Another eye witness said they saw a "cloud of smoke" before the air ambulance arrived.
Hamilton is expected to transferred to a hospital on the UK mainland to get further treatment on his unspecified injuries.
The Ballyclare man turned his attention to road racing after winning the British 600cc Superstock Championship in 2009.
He won the Best Newcomer Award at the Isle of Man TT in 2012 and has been a regular on the Irish national road racing scene in recent years.
Hamilton won the Irish Supersport and Supertwins Championships in 2013 while riding for the KMR Kawasaki team, run by Ryan Farquhar, who mentored him in the early part of his road racing career.
The racer equalled his best-ever TT finish with a fifth-place finish in this morning's Lightweight TT for Supertwins.
Last week, French rider Franck Petricola, became the 141st fatality at the races since they began in 1907.