Julie Gayet sues Closer over Hollande 'affair' report
The actress linked to French President Francois Hollande, Julie Gayet, is suing the magazine that published photos of their alleged affair.
Ms Gayet initiated proceedings against Closer for breach of privacy, the magazine told AFP news agency.
Mr Hollande decided not to sue the magazine after first threatening to.
The photos plunged the presidency into a crisis which saw Mr Hollande's current partner, Valerie Trierweiler, taken to hospital.
Ms Gayet, 41, is seeking 50,000 euros (£41,000; $68,000) in damages and 4,000 euros in legal costs from the magazine.
If she wins, Closer will have to publish the legal verdict on its cover page, AFP reports.
Mr Hollande, 59, told reporters on Tuesday he was experiencing a "difficult moment" in his private life but refused to answer questions over the report in Closer, saying "private matters should be dealt with privately".
Nor would he clarify whether Ms Trierweiler, 48, was still first lady before a February trip to the US.
Closer published a seven-page report on the alleged affair, which Mr Hollande has not denied, last Friday.
Photos show a man in a crash helmet on a moped, said to be Mr Hollande, visiting an apartment building near the Elysee Palace. Ms Gayet is shown at the building in a separate photo.
Public reaction to the alleged affair has been generally muted in France.
However, former President Nicolas Sarkozy has reportedly scoffed at the difficulties now being experienced by the man who defeated him in 2012.
"When you are president of the [French] Republic you have to be aware of the risk of looking ridiculous and these photos of Hollande in his motorbike helmet leaving his mistress's place has made him ridiculous," he was quoted as telling friends by satirical weekly Le Canard Enchaine.
Many believe Mr Sarkozy will stand for re-election in 2017, when he could again face Mr Hollande.