The woman had to take ten days off from work due to the injury.
According to French newspaper Sud Ouest, the injury was caused when a customer at a McDonald's store near the south-western city of Bordeaux grew angry at the slow speed of the service.
The impatient customer then hurled a potato wedge at a member of the staff.
However, the French fry missed the employee and instead splattered into the eye of the woman who was eating with her family at a nearby table, 'The Local' reported.
The woman reported the incident to police, but it remains unknown whether any action was taken.