Always a fighter defying the odds, the ambitious Le Pen set a new challenge for herself: "a profound reformation of our movement to constitute a new political force".
Macron will name his prime minister next week, but could be forced to amend his choice if the legislative elections don't go to plan.
This accelerated procedure, bypassing parliament, could mean a fiery start to his term as France's highly activist unions would likely bring protests out onto the streets, as they did previous year when Socialist Prime Minister Manuel Valls used the tactic.
Macron wants to cut unemployment to seven percent by 2022 by liberalising employment laws, cutting business rates and loosening restrictions in France's 35-hour working week. France's commitment to worldwide justice, through unambiguous political and financial support for the global Criminal Court (ICC), will be crucial in advancing the fight against impunity.
The two most optimistic possibilities for Macron is that En Marche! either secures a working majority in June or forms the biggest group of legislators but not an absolute majority.
Macron beat Le Pen by 66 percent to 34 on a platform of market-friendly reform and closer European integration.
Claiming a "massive" result of 10.64 million votes - a record for the FN - she promised "a profound transformation" of the party to grow its appeal.
"I call on all patriots to join us", she said. The National Front has two lawmakers in the outgoing parliament but hopes for dozens in June.More news: Pittsburgh Penguins vs Washington Capitals in National Hockey League playoffs Game 7
The primary beneficiaries of discontent with Macron in coming months could be Le Pen and/or hard left veteran Jean-Luc Melenchon, who finished fourth in last month's first round presidential elections.
A key danger for Macron in this scenario is that he could well fail, politically, to realise the expectations that are held about his new centre ground presidency.
Macron's main message has been his awareness of the divisions in French society.
"It requires that we moralize public life, defend our democratic vitality, reinforce our economy, construct new protection from the world that surrounds us, and give a place to everyone to rebuild our Europe and guarantee the security of all French people", Macron declared.
The euro fell the most against the dollar since late March, having risen in overnight trade to just above $1.10 when opinion polls signaled the scale of Macron's victory over anti-euro nationalist Marine Le Pen.
"Macron is a giant with feet of clay, elected without real desire of enthusiasm", he said. "I am not one of those who believes Macron is the answer to all of Europe's problems".
Macron, leader of the center-left En Marche!
Several veteran Socialists have already said they are ready to work with him.