The frontrunners will battle Benoit Hamon of the Francois Hollande’s Socialist Party and far-left candidate Jean-Luc Melenchon in a landmark TV debate later.
The debate will start at 8pm local time (9pm GMT) on one of the major film stages of La Plaine Saint-Denis in the Paris region.
How to watch the French election debate?
People living in France can watch the debate in French on French television channels TF1 and LCI.
France 24 will air the debate in English. You can watch the France 24 live stream here.
How will the French election debate work?
The programme will be divided into three main sections, which are expected to last about 50 minutes each.
The first part will look at French society and issues related to security, immigration, identity, ecology and institutions.
The second section takes a look at the economy and is a chance for candidates to debate labour issues, social protection, taxation and international trade.
The third and final part of the debate widens the conversation to France’s place in the world in relation to Europe, borders and terrorism.
Who is leading in the polls?
Front National (FN) populist Marine Le Pen looks set to win the first round of voting in April, but is expected to lose the run-off in May.
Her main rival is Emmanuel Macron – the surprise contender in French election who left the French Socialist Party to set up his own movement.
Francois Fillon, the Republicans, was an early frontrunner but has become embroiled in a scandal over accusations that he paid his wife for a fake job.
Who are the other French election candidates?
Philippe Poutou of the New Anticapitalist Party, Jacques Cheminade of Solidarity and Progress and the unaffiliated centrist representative Jean Lassalle all qualified at the last minute.
The other contenders are nationalist Nicolas Dupont-Aignan from Stand up France, Nathalie Arthaud from the Workers’ Struggle and Francois Asselineau of Popular Republican Union.
The first round of the presidential elections will be held on April 23, and the final two candidates will qualify for a run-off on May 7.