The crash was reported on northbound Highway 101 just south of the Sonoma County line at about 7:45 a.m., CHP Officer Scott Cakebread said.
The male driver and sole occupant of a vehicle apparently lost control and overturned, Cakebread said.
The driver was declared dead at the scene.
No other vehicles appeared to have been involved.
A Sig-alert was issued at 9:54 a.m. and traffic was backed up about two miles from the scene of the crash.