The crash was reported around 2:45 a.m. near 465 Shrewsbury St. The 26-year-old Westborough rider was thrown from the motorcycle and died at the scene, Worcester police said.
The man's name has not been released.
An initial investigation found that the rider was traveling at an "extremely high rate of speed" when he hit a vehicle as it was turning left, Worcester police said. The car was damaged, but the people inside were not hurt.
Worcester police are investigating the crash.
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