The sale is the latest attempt to tempt passengers back onto the railways after the epidemic decimated business.
After virtually no trains ran during the lockdown, SNCF has built back up to a normal service, but has still seen a steep decline in customers, despite the summer holidays proving a temporary boost.
SNCF estimates that 16 million people travelled by train in France in July and August, down from a seasonal average of 25 million.
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The sale has begun on the SNCF website and covers all tickets booked for journeys between September 8th and November 2nd on the budget Ouigo services, which cover 41 destinations in France.
The tickets follow normal SNCF booking rules, which means they can be cancelled or exchanged free of charge up to 1 hour 30 mins before the time of travel.
The sale lasts until the end of Thursday, September 3rd.