The California Highway Patrol says it happened just before 6 am on W. Kearney Boulevard near Howard Avenue.
Officers say the woman, later identified as 27-year-old Maria Garcia, drifted onto the shoulder, over-corrected, and then went back off the road.
That is when officers say Garcia crashed into a tree.
Garcia was taken to Community Regional Medical Center, where she died.
It is not known if drugs or alcohol were factors in the crash.