Toronto is the most populous city in Canada and the capital city of the Canadian province of Ontario. With a population of 2,794,356 in 2021, it is the fourth-most populous city in North America. The city is the anchor of the Golden Horseshoe, an urban agglomeration of 9,765,188 people (as of 2021) surrounding the western end of Lake Ontario, while the Greater Toronto Area proper had a 2021 population of 6,712,341. As of 2024, the Golden Horseshoe had an estimated population of 11,139,265 people while the census metropolitan area had an estimated population of 7,106,379. Toronto is an international centre of business, finance, arts, sports, and culture, and is recognized as one of the most multicultural and cosmopolitan cities in the world.

Indigenous peoples have travelled through and inhabited the Toronto area, located on a broad sloping plateau interspersed with rivers, deep ravines, and urban forest, for more than 10,000 years. After the broadly disputed Toronto Purchase, when the Mississauga surrendered the area to the British Crown, the British established the town of York in 1793 and later designated it as the capital of Upper Canada. During the War of 1812, the town was captured by the United States after they won the Battle of York in 1813, after which it was largely burned down and plundered by the American troops. York was renamed and incorporated in 1834 as the City of Toronto. It was designated as the capital of the province of Ontario in 1867 during Canadian Confederation. The city proper has since expanded past its original limits through both annexation and amalgamation to its current area of 630.2 km² (243.3 sq mi).

The diverse population of Toronto reflects its current and historical role as an important destination for immigrants to Canada. About half of its residents were born outside of Canada and over 200 ethnic origins are represented among its inhabitants. While the majority of Torontonians speak English as their primary language, over 160 languages are spoken in the city. The city is governed by Toronto City Council, a unicameral body whose members are elected every four years. City council is composed of 25 councillors, who each represent a geographical ward, and the mayor of Toronto who serves as head of council and the chief executive officer of the municipal government.

Toronto is Canada's largest financial centre, and is home to the Toronto Stock Exchange, the headquarters of Canada's five largest banks, and the headquarters of many large Canadian and multinational corporations. Its economy is highly diversified with strengths in technology, design, financial services, life sciences, education, arts, fashion, aerospace, environmental innovation, food services, and tourism. In 2022, a New York Times columnist listed Toronto as the third largest tech hub in North America, after the San Francisco Bay Area and New York City. Toronto is also a prominent centre for music, theatre, motion picture production, and television production, and is home to the headquarters of Canada's major national broadcast networks and media outlets. Its varied cultural institutions, which include numerous museums and galleries, festivals and public events, entertainment districts, national historic sites, and sports activities, attract over 26 million visitors each year.

The word Toronto has been recorded with various spellings in French and English, including Tarento, Tarontha, Taronto, Toranto, Torento, Toronto, and Toronton. The most frequent early spelling, Taronto, referred to 'The Narrows', a channel of water through which Lake Simcoe discharges into Lake Couchiching where the Huron had planted tree saplings to corral fish at what is now the Mnjikaning Fish Weirs site in Orillia. This narrows was called tkaronto by the Mohawk, meaning 'where there are trees standing in the water', and was recorded as early as 1615 by Samuel de Champlain. The word Toronto, meaning 'plenty', also appears in a 1632 French lexicon of the Huron language, which is also an Iroquoian language. It also appears on French maps referring to various locations, including Georgian Bay, Lake Simcoe, and several rivers. A portage route from Lake Ontario to Lake Huron running through this point, known as the Toronto Carrying-Place Trail, led to widespread use of the name.

Archaeological sites show evidence of human occupation in the site that will later become Toronto dating back thousands of years. The Wendat, an Iroquoian speaking people, occupied the territory that will become Toronto for centuries from pre-European contact until the invasion and massacre by the Haudenosaunee from the south side of Lake Ontario between 1648 and 1650. By the 1660s, the Haudenosaunee established two villages within what is today Toronto, Ganatsekwyagon (Bead Hill) on the banks of the Rouge River and Teiaiagon on the banks of the Humber River. By 1701, the Mississaugas, an Anishinaabe speaking people from Northern Ontario, had displaced the Haudenosaunee, who abandoned the Toronto area at the end of the Beaver Wars, with most returning to their homeland in present-day New York state.

French traders founded Fort Rouillé in 1750 (the current Exhibition grounds were later developed there), but abandoned it in 1759 during the Seven Years' War. The British defeated the French and their indigenous allies in the war, and the area became part of the British colony of Quebec in 1763.

During the American Revolutionary War, an influx of British settlers arrived there as United Empire Loyalists fled for the British-controlled lands north of Lake Ontario. The Crown granted them land to compensate for their losses in the Thirteen Colonies. The new province of Upper Canada was being created and needed a capital. In 1787, the British Lord Dorchester arranged for the Toronto Purchase with the Mississaugas of the New Credit First Nation, thereby securing more than a quarter of a million acres (1000 km²) of land in the Toronto area. Dorchester intended the location to be named Toronto. The first 25 years after the Toronto purchase were quiet, although "there were occasional independent fur traders" present in the area, with the usual complaints of debauchery and drunkenness.