The stake - consisting of 73.4 million shares and estimated to be worth $2.69bn (Â£1.8bn) - has been sold to investment bank Goldman Sachs.
The sale comes as Canada's government attempts to balance its budget for the coming financial year.
Canada has suffered from the global slump in oil prices during the past year.
Canada's Minister of Finance, Joe Oliver, said that the country's stake in GM was always supposed to be temporary, with intentions to return the shareholding to the private sector eventually.
Canada acquired its stake in General Motors - whose brands also include Cadillac, Chevrolet and Buick -  in 2009 as part of the bailout package for the then struggling carmaker.
The Canadian government has sold its remaining stake in Detroit automotive giant General Motors.