Sunday's first round saw the candidates of the ruling Socialists, Benoît Hamon, and the mainstream right Republicans, François Fillon, eliminated, with the hard left's Jean-Luc Mélenchon close behind Fillon and way ahead of Hamon.
So, although Macron was a minister in the outgoing government and Le Pen's FN has been on the political scene since 1972, neither represent a party that has held the presidency or run the country before.
Many Socialists and Republicans on Monday called for a vote for Macron to stop Le Pen, whose party is strongly anti-EU and anti-immigrant.
Here are the two candidates' main policy differences:
Europe: Le Pen wants to negotiate leaving the euro single currency and the Schengen open-borders agreement, put France's membership of the European
Union to a referendum and scrap the Ceta free-trade deal with Canada; Macron wants a eurozone budget, parliament and finance minister and to keep Ceta.
Immigration: Macron promises to examine asylum applications within six months, wants a 5,000-strong European border police force and would make French language skills the main condition for obtaining French nationality. Le Pen wants to limit immigration to 10,000 people a year, suggested a moratorium on legal immigration during the campaign, proposes toughening conditions for political asylum and the rights of families to join their relations in France, would abolish the right to French nationality for people born in France to foreign parents, would ban illegal immigrants from regularising their situation, would deport foreigners who break the law and limit foreigners' access to health care.
Secularism and racism: Le Pen wants to ban the Islamic headscarf and the burkini swimming costume in public, encourage "national preference" in employment and hold a referendum on writing it into the constitution; Macron opposes extension of the headscarf ban to universities and promises to make the fight against discrimination a "national priority".
Employment and economy: Macron proposes to slash 120,000 public-sector jobs, while employing more police and teachers, have working hours and conditions negotiated at company level, maintain retirement at 62, reduce employers' taxes and social security contributions and employees' social security contributions, cut off unemployment benefit for anyone refusing two "decent" offers of work, reduce the budget deficit to the EU's three percent limit and keep the current government's controversial labour reform; Le Pen promises to keep the 35-hour week, restore retirement at 60, raise small pensions, increase employment in health care, the police force and customs inspection, tax the products of companies who have relocated out of France at 35 percent, cut taxes for the lowest incomes and ignore EU budget restrictions.
Energy and agriculture: Le Pen would cut VAT on French livestock production, enforce geographical origin labelling of foodstuffs, keep nuclear power and suspend wind power; Macron would reduce nuclear power to 50 percent of France's energy supply, develop renewables and reform the EU's common agricultural policy.
International relations: Macron opposes new countries joining the Nato military alliance and wants a tough stance towards Russia; Le Pen wants to pull out of its intefrated command and improve relations with Russia.
To read our coverage of France's 2017 presidential election click here