It's the last chance for either candidate to convince voters ahead of Sunday's election that they are qualified to lead a nation, which has become increasingly fractured over the current government's inability to cope with concerns around immigration, integration and an ailing economy.
Polls suggest Macron will triumph in the election, but the specter of a mass voting boycott remains and it's something both candidates are desperate to address.
The debate marks the first time a French presidential runoff candidate has accepted an invitation to debate a far-right opponent.
In 2002, Le Pen's father and founder of the National Front, was denied the opportunity to debate Jacques Chirac after the eventual president refused to appear on stage with him, citing his opponent's extremist views.
Macron is instead seeking to undo Le Pen's arguments one by one on air.
Most had expected that Le Pen
, a former lawyer, would shine in the debates, yet, it has been Macron
, the lesser experienced of the two, who has outshone his opponent in larger format events to date.
Wednesday's debate will be his most difficult test yet. It will require him to keep his cool in what is likely to be a barrage of criticism from Le Pen.
Both Macron and Le Pen will be attempting to persuade the seven million or so voters who backed Jean-Luc Mélenchon
in the first round. The far-left firebrand has so far refused to endorse either candidate.
Many see Macron as a millionaire, former investment banker and economy minister, who remains very much part of the "elite."
They are unsure as to how he will actually govern given he is not backed by a political party; critics also point out his lack of experience.
Le Pen's challenge
However there are plenty of people who say they could never vote for Le Pen and since the conclusion of the first round of voting, she has been attempting to widen her appeal.
Last month, she announced that she had temporarily stepped down as leader of the National Front, painting herself as an independent candidate.
What the first round results showed is that she needs to reach out and perhaps play down more extreme parts of her campaign.
She has toned down the prospect of "Frexit" -- France's departure from the European Union -- and has also courted the voters of failed Republican candidate Francois Fillon.
On Tuesday, she gave a speech, which drew accusations of plagiarism
. Her camp defended it saying it was "a nod to Fillon" rather than Le Pen ripping him off, but she can ill afford any further slip-ups.
Perhaps her biggest challenge will be coming across as cool and calm and resisting the temptation to go after Macron.
There is no love lost between the two. Last week, when asked what she admired about her opponent, Le Pen commented: "Nothing. Absolutely nothing."
Pressure points for both
The debate will take in 10 different areas of policy including the economy, security and Europe.
Macron's weak spot is his lack of parliamentary machinery. Le Pen is almost certain to attack him on the subject, especially as she has confirmed that her prime minister would be DuPont Aignan, the right-wing leader of the "Stand up for France" party.
She will also aim to expose the lack of clarity in his campaign.
Le Pen will be attacked over Europe and her apparent flip-flopping.
And she is likely to be tackled on the subject of anti-Semitism after her campaign was hit by allegations of Holocaust denial
On Wednesday night, Macron needs to present himself as a president would, keep his cool, and not be drawn into a situation where he could lose his temper.
Le Pen is expected use the opportunity to ask the electorate to believe her claim that she has moved away from the far-right rhetoric of her father and become more mainstream.
For many, such an ask will be a step too far.
And so, with just four days to go, this will be her final chance to change perceptions and perhaps make this race far more uncomfortable for Macron than many were expecting.