"Neither of the right, nor the left" in his own words, Emmanuel Macron is a 39-year-old former banker hoping to convince the French to take a chance on his brand of youthful optimism.
He has never been elected and only launched his party last April, but polls currently show Macron as one of the frontrunners in the two-stage election on Sunday and on May 7.
After quitting his job as economy minister under unpopular Socialist President Francois Hollande in August, he has concentrated on building up his own centrist political movement "En Marche" ("On the Move").
The lover of poetry, who is married to his former school teacher, was initially dismissed by sceptics as appealing to a narrow band of young, urban professionals. But packed rallies and voter surveys have shown otherwise.
"We can't respond with the same men and the same ideas," Macron said as he launched his presidential bid in November at a jobs training centre in a gritty Parisian suburb.
With frustration at France's political class running high, Macron has tapped into a desire for wholesale change that has also propelled far-right candidate Marine Le Pen and leftist Jean-Luc Melenchon.
"I'm here because he's young, he's dynamic. It's like a breath of fresh air," 23-year-old shop worker Marine Gonidou told AFP at a rally in Brittany in January.
At 39, Macron would be the youngest French leader in modern history, upending tradition that has seen voters favour experience in their powerful presidents.
Although positioned as an outsider, the brilliant student followed a well-worn path through elite French universities including ENA, the administration school that has groomed many a French leader.
After going into banking, where he earned nearly 2.4 million euros ($2.6 million) from 2011-2012 at Rothschild, Macron became an economic advisor to Hollande in 2012 and then economy minister two years later.
Despite the efforts of his opponents, "he seems to have escaped his association with the government," said Dominique Reynie, head of the Foundation for Political Innovation think-tank in Paris.
The outcome of the election will be the ultimate test of his claim that France is "contrarian" -- ready to elect a pro-EU, pro-globalisation liberal at a time when rightwing nationalists are making gains across the world.
European leaders in Berlin and Brussels will be hoping he is right.
As well as wanting to improve the business environment, Macron stresses the need to boost education in deprived areas and has spoken out against stigmatising Muslims with France's strict rules on secularism.
His championing of tech firms and the "Uber-isation" of the economy, in which people increasingly work as independents rather than as employees, has helped burnish his image as a moderniser.
"I want us to be able to start a business more easily, to innovate more easily" is one of his mantras, explained in depth in his pre-election book "Revolution".
After looking the most likely next president for the last few months, polls have shown the race tightening in recent weeks and another terror attack on Thursday could work against the inexperienced maverick.
Opponents still dismiss him as deliberately vague, with far-right leader Marine Le Pen landing a blow during a televised debate in March when she attacked him for waffling.
"Mr Macron you have an amazing talent, you've spoken for seven minutes and I'm unable to resume your thinking. You've said nothing!" she said.
In his personal life, Macron is anything but orthodox.
The theatre lover from a middle-class family in northeast France fell in love with his secondary school drama teacher, Brigitte Trogneux, in a story that has captivated the French media.
Trogneux, a mother of three children 24 years older than him, went on to divorce her husband and marry the young prodigy in 2007.
"At the age of 17, Emmanuel said to me: 'Whatever you do, I will marry you!'," Trogneux told Paris Match magazine last April.
Some have found the relationship difficult to believe despite numerous appearances together in glossy magazines, forcing Macron to repeatedly laugh off rumours he is gay.
While at ease among ordinary voters and charismatic, Macron has been accused of being condescending in the past, whether referring to "illiterate" abattoir workers, "alcoholic" laid-off workers or the "poor people" who travel on buses.
In an infamous exchange, when confronted by a protester in a T-shirt in May last year, he lost his cool, saying: "The best way to buy yourself a suit is to work."