According to investigators, a van was heading west on Concession Road 9, east of Sideline 32, when it lost control shortly after 3 a.m.
Police say the van entered a ditch and then struck a tree.
The driver was pronounced dead at the scene.
Police say the driver was a 51-year-old woman from Stouffville, Ont. Her name has not been released.
Investigators would like to hear from anyone who has information about the crash.