"I want to be the president of the patriots against the threat of nationalists," the 39-year-old former banker told hundreds of flag-waving supporters.
"In your name, I will be... the voice of hope for our country and for Europe," said Macron, who had never before stood for election and only started his centrist movement 12 months ago.
He will meet Le Pen in the May 7 second round, according to the projections.
The French vote on Sunday was being closely watched as a bellwether for populist sentiment following the election of Donald Trump as US President and Britain's vote to leave the EU.
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