The first accident happened just after 1 a.m. when a motorcycle rider travelling eastbound on the Gardiner Expressway lost control near the Humber Bridge.
The rider, a man in his 30s, hit a barrier and was tossed into the westbound lanes of the expressway where he was struck by several vehicles. He was pronounced dead at the scene.
Police believe the motorcycle was travelling at a high rate of speed. The accident closed the Gardiner until just after 7 a.m.
Just before 8 a.m., a 52-year-old Bramalea woman died when the disabled car she was driving was rear-ended by a garbage truck travelling on Highway 407 between Bathurst and Yonge.
She was taken to hospital and pronounced dead shortly after.
Two people died and a third is in hospital with critical injuries after a collision on Highway 403 near Winston Churchill Boulevard at around 3:45 p.m.
The OPP say it appears an SUV struck a tractor-trailer while trying to merge onto the highway. The driver of the tractor-trailer was not hurt. The crash caused an hours-long closure of all eastbound lanes of Highway 403.