Emmanuel Macron and his wife Brigitte intend to submit photographic and scientific evidence to a US court to show that Mrs Macron is a woman.
Their lawyer said they will present the documentation in a defamation suit they have taken against Candace Owens.
The American influencer promoted her belief that Mrs Macron was born male and her lawyers responded with a motion to dismiss the claim.
The Macrons' lawyer, Tom Clare, said the French First Lady had found the claims "incredibly upsetting" and they were a "distraction" to the French President.
Speaking to the BBC, he said: "I don't want to suggest that it somehow has thrown him off his game.
"But just like anybody who is juggling a career and a family life as well, when your family is under attack, it wears on you. And he's not immune from that because he's the president of a country."
Mr Clare said there will be "expert testimony that will come out that will be scientific in nature".
He did not reveal the exact nature of this but did claim the couple is prepared to demonstrate fully "both generically and specifically" that the allegations are false.
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Mrs Macron said the claims have been 'incredibly upsetting'
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He continued: "It is incredibly upsetting to think that you have to go and subject yourself to put this type of proof forward.
"It is a process that she will have to subject herself to in a very public way. But she's willing to do it. She is firmly resolved to do what it takes to set the record straight.
"If that unpleasantness and that discomfort that she has of opening herself up in that way is what it takes to set a record straight and stop this, she's 100 per cent ready to meet that burden."
When questioned if the couple would be providing photos of Brigitte pregnant and raising her children, Mr Clare said they existed and would be presented in court, where there are rules and standards.
Ms Owens, a former commentator for conservative US outlet Daily Wire with millions of social media followers, has repeatedly promoted her view that Brigitte Macron is a man.
In March 2024, she claimed to stake her "entire professional reputation" on the allegation.
The allegation came in fringe online spaces years earlier, notably through French bloggers Amandine Roy and Natacha Rey.
The Macrons initially won a defamation case in France against the pair, but that ruling was overturned on appeal in 2025 on freedom of expression grounds, not on the basis of truth. The Macrons are appealing the decision.
Emmanuel Macron called the claims 'nonsense'
| GETTYIn July, the Macrons filed a lawsuit against Ms Owens in the US, alleging she "disregarded all credible evidence disproving her claim in favour of platforming known conspiracy theorists and proven defamers".
US defamation cases against public figures require proof of "actual malice".
In August, Mr Macron said: "This is about defending my honour because this is nonsense.
"This is someone who knew full well that she had false information and did so with the aim of causing harm, in the service of an ideology and with established connections to far-right leaders."