Canadian whisky is whisky that by law must be mashed, distilled and aged at least three years in Canada in a wooden barrel of not greater than 700 L capacity. Most Canadian whiskies are blended multi-grain whiskies and are usually lighter and smoother than other whiskey styles. They are often colloquially and generically referred to (and may legally be labelled) as "rye whisky" in Canada, though the U.S. definition of "Rye Whiskey" would prevent lower-rye-content versions from being so labelled in the U.S.. Although rye is often a primary component in Canadian whiskies, the use of rye is not dictated by legal standards. In converse, the U.S. definition of "Rye Whiskey" does not have aging requirements, and younger (even Straight) U.S. versions would not legally be labelled "Rye Whisky" in Canada.
Canadian whisky featured prominently in illegal imports (known as bootlegging) into the U.S. during Prohibition in the 1920s. Hiram Walker had a distillery in Windsor, Ontario across the Detroit River from Detroit, Michigan that easily served small, fast smuggling boats.
There are other types of whiskies made in Canada, such as the "single malt" and "Quebec Maple" whiskies described below; but these are more boutique whiskies and are not necessarily included in the general category of Canadian whisky.