Minjee Lee has had to settle for a share of second place as Germany's Caroline Masson rattled home with nine birdies to claim her first LPGA Tour title.
Australian Lee shot a four-under-par 68 closing round on the Whistling Bear course in Ontario but 27-year-old Masson went one shot better with a 67 and won the Manulife Classic by one stroke.
Masson rebounded from an opening double bogey as she won from Lee, third-round leader Mi Hyang Lee of South Korea (71) and Solheim Cup teammate Karine Icher of France (66).
Masson joined Anna Nordqvist and Brittany Lang as the only players over 23 years old to win in the first 24 events this season - and also joined Nordqvist as the only European winners.
Thailand's Ariya Jutanugarn tied for fifth at 14 under in her bid to win three straight events for the second time this season. The second-ranked Jutanugarn made two late bogeys in a 70.
Top-ranked Lydia and 2015 winner Suzann Pettersen also were 14 under. Ko had a 68, and Pettersen finished with a 66.
Masson didn't make a par until the seventh hole, following the double bogey with three straight birdies, a bogey on No.5 and a birdied on the sixth.
The former Oklahoma State player had four straight birdies on Nos. 9-12, bogeyed the par-4 13th and birdied the par-5 16th. She birdied all four par 5s.
