All lanes of Highway 401 between Shannonville Road and Highway 49 at Marysville have been reopened.
The OPP made the announcement in a tweet just before midnight Thursday.
A collision involving two tractor trailers and a car closed the highway in both directions around 6:30 Thursday morning.
One person was killed and another seriously injured.
The 401 was blocked in both directions for much of the day but one westbound lane was reopened late in the afternoon.
Police are asking witnesses or anyone with dash cam footage to call them.
