The Ontario government says it will gain approximately $1.1 billion from the sale, adding that the funds will be invested to help build a "new generation" of public infrastructure.
Both Ottawa and the Ontario government acquired GM shares in 2009 after providing about $10.6 billion in aid to the automaker.
Ontario made $4.8 billion in financial assistance available to GM and Chrysler, in partnership with the federal government.
The provincial government says the gain on the sale of the shares exceeds the $900 million target included in the 2014 budget for 2014-15 net revenue gains from asset optimization.
Finance Minister Charles Sousa says Wednesday's sale marks an important step in unlocking the value of the province's assets to grow the economy and invest in public infrastructure.
"The Ontario government is proud to have been able to play an important role in protecting thousands of jobs across the province through its support of the auto sector in 2009," Sousa said in a release.