The prosecutor's office in the Paris suburb of Nanterre said the charges were issued for "distribution of violent images." If the case eventually reaches trial and she's convicted, Le Pen could face up to three years in prison and a 75,000-euro (USD 90,000) fine.
Le Pen's December 2015 tweets showed executions by IS extremists, including the killing of American reporter James Foley. She posted them in the wake of the November 2015 IS attacks on Paris, accusing the government of not doing enough to protect France.
Lawyer Rodolphe Bosselut, representing Le Pen in the case, confirmed the charges but wouldn't comment. It's one of multiple legal cases targeting Le Pen or the National Front.
In one high-profile investigation, she and the party have to respond to charges over the misuse of European funds. She denies wrongdoing.
Marine Le Pen's French-first, Islam-skeptic nationalism resonated widely in the wake of Donald Trump's election and Britain's vote to leave the European Union.