Toronto is the largest city in Canada and is the provincial capital of Ontario. It is located 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 south-central Ontario known as the Golden Horseshoe which is home to 8.1 million residents. 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 cities 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 a majority 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 percent of the population were born outside of Canada. Because of the city's low crime rates, clean environment, generally high standard of living, and friendlier attitudes 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.

The city is intersected by two rivers and numerous tributaries: the Humber River in the west end and the Don River east of downtown at opposite ends of the Toronto Harbour. The harbour was naturally created by sediment build-up from lake currents that created the Toronto Islands. The many creeks and rivers cutting from north toward the lake created large tracts of densely-forested ravines, and provide ideal sites for parks and recreational trails. However, the ravines also interfere with the city's grid plan, and this results in major thoroughfares such as Finch Avenue, Leslie Street, Lawrence Avenue, and St. Clair Avenue terminating on one side of ravines and continuing on the other side. Other thoroughfares such as the Bloor Street Viaduct are required to span above the ravines. These deep ravines prove useful for draining the city's vast storm sewer system during heavy rains but some sections, particularly near the Don River are prone to sudden, heavy floods. Storage tanks at waste treatment facilities will often receive too much river discharge causing them to overflow, allowing untreated sewage to escape into Lake Ontario closing local beaches for swimming.

During the last ice age, the lower part of Toronto was beneath Glacial Lake Iroquois. Today, a series of escarpments mark the lake's former boundary, known as the Iroquois Shoreline. The escarpments are most prominent from Victoria Park Avenue to the mouth of Highland Creek, where they form the Scarborough Bluffs. Other noticeable sections include the area near St. Clair Avenue West between Bathurst Street and the Don River, and north of Davenport Road from Caledonia to Spadina Avenue, the Casa Loma grounds sit above this escarpment. Although not remarkably hilly, Toronto does have elevation differences ranging from 75 metres (246 ft) above-sea-level at the Lake Ontario shore to 270 m (886 ft) ASL near the York University grounds in the city's north end.

Much of the current lakeshore land area fronting the Toronto Harbour is actually artificial landfill. In the mid-19th century the lakefront was set back up to 1 kilometre (0.6 mi) further inland than it is today. Much of the Toronto harbour (the quays, formerly known as wharves) and adjacent Portlands are also fill. The Toronto Islands were actually a landspit until a storm in 1858 severed its connection to the mainland, creating a channel later used by shipping interests to access the docks.

Toronto is a major scene for theatre and other performing arts, with more than fifty ballet and dance companies, six opera companies, and two symphony orchestras. The city is home to the National Ballet of Canada, the Canadian Opera Company, and the Toronto Symphony Orchestra. Notable performance venues include the Four Seasons Centre for the Performing Arts, Roy Thomson Hall, the Princess of Wales Theatre, the Royal Alexandra Theatre, Massey Hall, the Toronto Centre for the Arts, the Elgin and Winter Garden Theatres and the Hummingbird Centre (formerly the "O'Keefe Centre"). Ontario Place features the world's first permanent IMAX movie theatre, the Cinesphere, as well as the Molson Amphitheatre, an open-air venue for large-scale music concerts. Each summer, the Canadian Stage Company presents an outdoor Shakespeare production in Toronto's High Park called "Dream in High Park". Canada's Walk of Fame acknowledges the achievements of successful Canadians, with of a series of stars on designated blocks of sidewalks along King Street and Simcoe Street.

The Distillery District is a pedestrian village containing boutiques, art galleries, restaurants, artist studios and small breweries, including the well-known Mill Street Brewery. A new theatre in the district, the Young Centre for the Performing Arts, is the home of the Soulpepper Theatre Company and the drama productions of nearby George Brown College.

The production of domestic and foreign film and television is a major local industry. Many movie releases are screened in Toronto prior to wider release in North America. The Toronto International Film Festival is one of the most important annual events for the international film industry. Europe's largest film studio, Pinewood Studios Group of London, is scheduled to open a major new film studio complex in west-end Toronto, with five sound stages, with the first two to open by fall 2008.

Toronto's Caribana festival takes place from mid-July to early August of every summer, and is one of North America's largest street festivals. For the most part, Caribana is based on the Trinidad and Tobago Carnival, and the first Caribana took place in 1967 when the city's Caribbean community celebrated Canada's Centennial year. 40 years later, it has grown to attract one million people to Toronto's Lake Shore Boulevard annually. Tourism for the festival is in the hundred thousands, and each year, the event brings in about $300 million.