It happened on a section of the freeway before Brock Road, shortly after 5:30 a.m. Friday.
An Ornge ambulance spokesman said they had been called to the motorway for a collision with a motorcycle.
A man was airlifted to a Toronto hospital with serious injuries, Ornge said.
The cause of the collision is unknown.
Ontario District Police closed the west lanes of Westney Road. It has not been estimated when the lanes will reopen.
“There are long delays in the area. The investigation is ongoing,” said OPP Sgt. said Kerry Schmidt. “I expect the closure to remain in place for some time.”