Police said 350,000 people were expected to march and 21,000 officers had been mobilized after labor unions, student groups and rights groups called for rallies to oppose the anti-immigration, eurosceptic RN ahead of upcoming elections to the French parliament, Reuters reported.
At least 150 marches were expected across France in cities including Marseille, Toulouse, Lyon and Lille.
In Paris where up to 100,000 people were expected to turn out a march will set off at 1200 GMT from Place de La Republique, in the east, going through the Bastille square to Nation.
President Emmanuel Macron called a snap legislative election, to be held in two rounds on June 30 and July 7, after his centrist alliance was trounced by the RN in last Sunday's European Parliament ballot.
A first series of opinion polls have projected that the RN could win the legislative election and be in a position to run the government.
A poll conducted for Le Point magazine published on Friday forecast RN would lead in the first round of the parliamentary election with 29.5% of votes, narrowly ahead of a coalition of left-wing parties called the Popular Front on 28.5%.
Macron's centrist camp was on 18%.
At least two polls have put the left not far behind the RN and ahead of Macron's group.