The provincial police said they responded to a number of fatal accidents over the long weekend, while more than 10,000 traffic and transportation charges were issued.
Ontario Provincial Police said three people were killed in separate traffic accidents.
Two of the dead were motorcyclists.
Two people were also killed in maritime incidents, police said, one involving a motorboat capsizing and the other involving a person falling from a stand-up paddle board.
A sixth person died in an all-terrain vehicle crash. More than 10,000 traffic and transportation related charges were issued by OPP between Friday afternoon and Monday evening, including 5,847 speeding charges and 138 stunt driving/racing charges.
Other charges include 458 counts of not wearing a seat belt, 192 counts of drunk driving and 101 counts of distracted driving.