Brigitte Macron is set to take legal action over an internet conspiracy theory that she is a transgender woman and was born male, reports BBC News.
The French first lady has been targeted on social media with the false claims, after they were published on a far-right website in September then circulated by conspiracy theorists.
The rumours claim she was born male under the name Jean-Michel Trogneux.
The name has trended on social media with tens of thousands of mentions.
A lawyer for Mrs Macron - who is the mother of three adult children from her first marriage - confirmed she is taking action.
"She has decided to initiate proceedings, it is in progress," lawyer Jean Ennochi confirmed to the AFP news agency.
The lies about the 68-year-old have been spread by accounts opposed to her husband, President Emmanuel Macron, including those on the political far-right, anti-vaccine groups and from the QAnon conspiracy movement.
French media have traced the story to an article written on a far-right journal by a woman named Natacha Rey.