Jutta Merilainen of Batawa, Ont., finished the 42.2-kilometre course in three hours and 44 seconds, according to results tweeted by GoodLife.
David Le Porho of Montreal was the first male runner to finish up the race. His finish time was just under 2 hours and 22 minutes.
The marathon website indicates that some 2,500 people were expected to run the marathon on Sunday. The course started at Mel Lastman Square and ended at Ontario Place.