Toronto (pronounced /təˈrɒntoʊ/, colloquially /ˈtrɒnoʊ/ or /təˈrɒnoʊ/) is the most populous city in Canada and the provincial capital of Ontario. It is located in Southern Ontario on the northwestern shore of Lake Ontario. With over 2.5 million residents, it is the fifth most populous municipality in North America. Toronto is at the heart of the Greater Toronto Area (GTA), and is part of a densely populated region in Southern Ontario known as the Golden Horseshoe, which is home to 8.1 million residents and has approximately 25% of Canada's population.  The census metropolitan area (CMA) had a population of 5,113,149, and the Greater Toronto Area had a population of 5,555,912 in the 2006 Census.

As Canada's economic capital, Toronto is considered a global city and is one of the top financial centres in the world.  Toronto's leading economic sectors include finance, business services, telecommunications, aerospace, transportation, media, arts, film, television production, publishing, software production, medical research, education, tourism and sports industries.  The Toronto Stock Exchange, the world's seventh largest, is headquartered in the city, along with most of Canada's corporations.

Toronto's population is cosmopolitan and international,  reflecting its role as an important destination for immigrants to Canada. Toronto is one of the world's most diverse cities by percentage of non-native-born residents, as about 49% of the population were born outside of Canada. Because of the city's low crime rates, clean environment, high standard of living, and friendly attitude to diversity, Toronto is consistently rated as one of the world's most livable cities by the Economist Intelligence Unit and the Mercer Quality of Living Survey. In addition, Toronto was ranked as the most expensive Canadian city in which to live in 2006.  Residents of Toronto are called Torontonians.