Ontario is one of the thirteen provinces and territories of Canada. Located in Central Canada, it is Canada’s most populous province, with 38.3 percent of the country’s population, and is the second-largest province by total area (after Quebec). Ontario is Canada’s fourth-largest jurisdiction in total area when the territories of the Northwest Territories and Nunavut are included. It is home to the nation’s capital city, Ottawa, and the nation’s most populous city, Toronto, which is Ontario’s provincial capital. The flag of Ontario is the provincial flag of Ontario, Canada. It is a defaced Red Ensign, with the Royal Union Flag in the canton and the Ontario shield of arms in the fly. The flag of Ontario was derived from the Canadian Red Ensign, which was used as a civil ensign and as a de facto flag of Canada from the late 19th century to 1965. 4K Resolution.