The online news portal of TV5
In rising to the party's leadership, Wynne becomes the next prime minister of Ontario -- and will also be the first woman to hold the post in Canada's most populous province.
"The province has changed, our party has changed," Wynne was quoted as saying by CBC News.
"I do not believe that the people of Ontario... hold that prejudice in their hearts," she said of her sexual orientation.
Wynne, who has three children from a previous marriage, now lives with a woman.
Four other provinces and one territory are already led by women, including Alberta, British Colombia, Newfoundland and Labrador, Quebec, and Nunavut.
Canada is composed of 10 provinces and three territories.