Thunderstorms in southern Ontario, Canada, spawned at least three tornadoes that caused over C$500 million in damage.

Ontario is the southernmost province of Canada. Located in Central Canada, Ontario is the country's most populous province. As of the 2021 Canadian census, it is home to 38.5% of the country's population, and is the second-largest province by total area. Ontario is Canada's fourth-largest jurisdiction in total area of all the Canadian provinces and territories. It is home to the nation's capital, Ottawa, and its most populous city, Toronto, which is Ontario's provincial capital.

The Southern Ontario tornado outbreak of 2005 was a series of thunderstorms on the afternoon of August 19, 2005, that spawned tornadoes damaging homes in the Conestoga Lake, Fergus, and Tavistock areas. A tornado was reported within the Toronto city limits, although this was never officially confirmed by the Meteorological Service of Canada. The storms morphed into heavy rain cells when reaching Toronto. The Insurance Bureau of Canada has estimated that insured losses were the highest in the province's history, exceeding 500 million Canadian dollars, two and a half times that of Ontario's losses during the 1998 ice storm and the second largest loss event in Canadian history until another event of torrential rain of July 8, 2013.

The Canadian dollar is the currency of Canada. It is abbreviated with the dollar sign $. There is no standard disambiguating form, but the abbreviations Can$, CA$ and C$ are frequently used for distinction from other dollar-denominated currencies. It is divided into 100 cents (¢).