MONTREAL, QUEBEC--(Marketwire - May 31, 2011) -

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Osisko Mining Corporation ("Osisko") (TSX:OSK)(FRANKFURT:EWX), a leader in exploration and mining in Quebec, proceeded yesterday with the official inauguration of the Canadian Malartic gold mine, a large-scale open pit mine located in Malartic, Abitibi.

For this event, members of Osisko's Board of Directors and its management team welcomed several guests, including Messrs. Clément Gignac, Quebec's Minister of Economic Development, Innovation and Export Trade; Pierre Corbeil, Minister of Agriculture, Fisheries and Food, Minister responsible for the Abitibi-Témiscamingue and Nord-du-Québec regions and MP for Abitibi-Est; Serge Simard, Minister for Natural Resources and Wildlife; and André Vezeau, Mayor of Malartic.

"Today, we celebrate a new beginning for mining in Malartic", stated Sean Roosen, President and CEO of Osisko. "With the commissioning of the Canadian Malartic mine, the Town of Malartic returns to its rightful place as one of the major gold mining centres in Canada."

Mr. Roosen reminded those in attendance that the success of this billion-dollar-plus project was the result of a collaborative effort involving thousands of people. He particularly emphasized the support from the Town of Malartic and its citizens, and the skills and expertise of Osisko's employees and contractors. He also acknowledged the positive attitude of the Quebec government, always acting in the best interests of its citizens and their environment while adopting a "problem-solving" approach.

About Canadian Malartic

Canadian Malartic is Osisko's first mine to go into production. Osisko estimates it will extract more than 9 million ounces of gold at Canadian Malartic from now until 2027. The mine currently employs 465 people.

Requiring investments of about one billion dollars, the Canadian Malartic Project generated substantial benefits all across Quebec and particularly in the Abitibi-Témiscamingue region, where $500 million of this investment was spent. Osisko received many awards for its project, in recognition of its firm commitment to the principles of sustainable development.

About Osisko Mining Corporation

Established in 1998, Osisko is based in Montreal. Initially focusing on mineral exploration, the company evolved into a mining corporation when it decided to develop the Canadian Malartic Project on its own. Osisko is still involved in mineral exploration in the Abitibi region of Quebec, in Nova Scotia and in Northwestern Ontario with the Hammond Reef Project.

Osisko employs more than 650 people, including employees working at the Canadian Malartic mine.

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Contact Information:

John Burzynski
Vice-President Corporate Development
(416) 363-8653

Sylvie Prud'homme
Investor Relations
(514) 735-7131
Toll Free: 1-888-674-7563