Who was the French explorer who first explored Canada?

Jacques Cartier

Wrong. Jacques Cartier explored the fleuve St. Laurent, in Quebec. He traveled from France to Canada on three separate journeys, exploring what is now Quebec. He never went all the way across Canada.

The first explorer to make it all the way across Canada on land was Sir Alexander MacKenzie. He reached Bella Coola, British Columbia on the 22nd of July, 1793. On a rock along the coast he carved "Alex MacKenzie from Canada by land 22d July 1973.