In a solemn speech, Macron addressed "republican greetings" to his defeated rival, Marine Le Pen, and had a message for those who "voted for the extremes", a reference to both Le Pen and hard-left candidate Jean-Luc Mélenchon.
He had "heard their anger, their anxiety, their doubts", he said and promised "I will fight the divisions that are undermining France."
Mélenchon prepares parliamentary election
Shortly afterwards Mélenchon said that the country had "massively rejected" the extreme right but accused Macron of planning war against social gains and the ecology and called on his seven million voters to mobilise for June's parliamentary elections.
Le Pen earlier said that she planned to reform her movement to create a "new political force".
Macron promises to change EU
On the European Union, one of his main differences with Le Pen, the new president promised to "restore the links between Europe and its citizens".
"Let us love France," Macron concluded. "I will serve her with humility, devotion and determination."
The euro rallied to 1.1010 dollars from 1.0998 dollars in early forex trading in Asia.
Bosses' union Medef congratulated the new president, saying he had an "immense task" ahead of him.
The French have chosen a "European future", European Commission President Jean-Claude Juncker declared.
US President Donald Trump tweeted his congratulations.
"I look very much forward to working with him!" he said.
Macron will name his interim prime minister in a week's time, his party's spokesperson said.
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