The charges relate to the misuse of over €3 million of European Parliament funds between 2004 and 2016.
Ms Le Pen has been handed a four-year jail sentence, of which two years are suspended, and banned from public office for five years, excluding her from the 2027 presidential election.
Ms Le Pen, who was a prominent contender to succeed Emmanuel Macron, denies the charges and claims a political plot against her.
The verdict could significantly impact the French political landscape.