Ontario

American  

[on-tair-ee-oh] / ɒnˈtɛər iˌoʊ /

noun

1. a province in southern Canada, bordering on the Great Lakes. 412,582 square miles (1,068,585 square kilometers). Toronto.

2. Lake Ontario, a lake between the northeastern United States and southern Canada, between New York and Ontario province: the smallest of the Great Lakes. 193 miles (310 kilometers) long; 7,540 square miles (19,530 square kilometers).

3. a city in southwestern California, east of Los Angeles.

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Ontario British  

/ ɒnˈtɛərɪəʊ /

noun

1. Abbreviation: Ont..   ON.  a province of central Canada: lies mostly on the Canadian Shield and contains the fertile plain of the lower Great Lakes and the St Lawrence River, one of the world's leading industrial areas; the second largest and the most populous province. Capital: Toronto. Pop: 12 392 721 (2004 est). Area: 891 198 sq km (344 092 sq miles)

2. a lake between the US and Canada, bordering on New York State and Ontario province: the smallest of the Great Lakes; linked with Lake Erie by the Niagara River and Welland Canal; drained by the St Lawrence. Area: 19 684 sq km (7600 sq miles)

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Ontario Cultural  

1. Province in central Canada, bordered by Hudson Bay and James Bay to the north; Quebec to the east; the St. Lawrence River, Lake Ontario, Lake Erie, Lake Huron, Lake Superior, and Minnesota to the south; and Manitoba to the west. Its capital and largest city is Toronto.

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Discover More

Ontario is the most heavily industrialized, populous, and prosperous province in Canada.

The Canadian side of Niagara Falls is in southern Ontario.

Ottawa, Canada's capital, is in southeastern Ontario.

Other Word Forms

• Ontarian
  adjective
• Ontaric
  adjective

Example Sentences

See Examples For:

Ontario

He played four seasons in the Ontario Hockey League and one at Clarkson University last season before transferring to Arizona State.

From Los Angeles Times ● Sep. 4, 2026

Toronto and parts of southern Ontario, Canada, were hit by powerful thunderstorms bringing torrential rain, large hail and damaging winds.

From BBC ● Sep. 3, 2026

Carney said this marks the first time the railcars would be built exclusively in Canada, with work done at the French company’s operations in suburban Montreal and northern Ontario.

From The Wall Street Journal ● Sep. 3, 2026

"Let's be serious. Long before President Trump, this lake was called Lake Ontario. And long after President Trump is gone, it will still be called Lake Ontario," Ontario premier Ford said.

From Barron's ● Sep. 2, 2026

But also I’m cheesed off because the Art Gallery of Ontario wouldn’t do it.

From "Cat's Eye" by Margaret Atwood