The 49-year-old leader of France’s far-right Front National has been charged over images she posted on the social media site showing gruesome atrocities allegedly carried out by the terror group.
She faces facing charges of circulating “violent messages that incite terrorism or pornography or seriously harm human dignity”, and that can be viewed by a minor.
The crime is punishable by up to three years in prison and a fine of €75,000 (£66,000).
Ms Le Pen, long seen as the face of Europe’s anti-immigrant populism, posted three graphic images of purported Islamic State executions on Twitter in December 2015, including the beheading of American journalist James Foley.
The others showed a man being burnt alive, and another showed a man in an orange jumpsuit being driven over by a tank.
She captioned the images “Daesh is THIS”, using the Arabic acronym for ISIS, in response to a journalist comparing extremists and the French far right.
She posted them in the wake of the Paris terror attack in November 2015, accusing the government of not doing enough to protect France.
Her posts were greeted with considerable backlash and Mr Foley’s parents said they were “deeply disturbed” their son’s photograph was used.
Ms Le Pen later deleted the picture after a request from his family, saying she had been unaware of his identity.
Speaking to AFP, she said: “I am being charged for having condemned the horrors of Daesh. In other countries this would have earned me a medal.”
Ms Le Pen has previously denounced the investigation into the tweets as “political interference”, but did not immediately comment publicly on the charges.
As deputy in the National Assembly, Ms Le Pen is afforded some immunity from prosecution, but European Union lawmakers lifted the EU parliamentary immunity allowing legal action to be taken.
Ms Le Pen’s immunity has been lifted before, in 2013, by the EU Parliament.
She was then prosecuted in 2015 with “incitement to discrimination over people’s religious beliefs”, for comparing Muslims praying in public to the Nazi occupation of France during World War Two.
Prosecutors eventually recommended the charges be dropped.
This is the latest blow for the controversial politician as her party is in crisis after she lost her bid for the French presidency to Emmanuel Macron last year.