Ontario Nature is a non-profit organization based in Toronto that promotes the preservation and conservation of natural areas in the Canadian province of Ontario. It was established in 1931 as the Federation of Ontario Naturalists and changed its name to Ontario Nature in 2004.
Ontario Nature maintains its own system of 24 nature reserves, totalling 2,788 hectares. It creates parks and nature reserves. It also provides public education about nature. Ontario Nature publishes a quarterly magazine called ON Nature, formerly called Seasons.