He is the most successful athlete in Olympic history.
Swimmer Michael Phelps, 29, was in the news when he was arrested for driving under the influence (DUI) in September, and suspended for six months by USA Swimming.
Now his self-proclaimed girlfriend, Taylor Lianne Chandler, has made a shocking admission, the Mail Online reported.
She said she was born intersex and lived as a boy until her teens, and that her birth name was David Roy Fitch.
She told entertainment website RadarOnline: "I was born with male genitalia with no testicles, but I also have a uterus and no ovaries."
She decided to change her name as a teenager when she went on testosterone blockers and later underwent surgery to become a woman.
Ms Chandler, 41, claims that Phelps was unaware that she was born intersex and that she did not tell him during their relationship.
She explained in a Facebook post: "I was never a man, never lived as a man. No one can say they knew me as a man or produce a photo of me as a man."
She added: "There are people that remember me as an androgynous child at times because of what was forced upon me."
She said she fell in love with Phelps after they met on Tinder, a matchmaking mobile app.
"Spending time with him was like a teenage love affair," she was quoted as saying.
In an interview with the National Enquirer magazine, she talked about her first date with the swimming superstar - they went for a football game.
"One thing led to the next, and we made love during halftime," she claimed in the interview.
"Later, we had sex again. The intimacy with him was amazing! It was the first time in my life that someone had made me feel like a true woman."
Ms Chandler claims she was with Phelps when he was arrested on Sept 30 in Baltimore, Maryland.
The swimmer entered rehab just a few days after the incident and completed his programme, she claimed.
In her post, Ms Chandler also talked about the difficulties she faced in her life.
She said: "My birth certificate was modified along with my name while I was a teenager, prior to any corrective surgery. I originally changed my name to Paige Victoria Whitney.
"I had already left home at 15. At 18 I got in trouble twice, once for a bad cheque and then a DUI.
"At 19, I thought it would be smart to blackmail someone into giving me the money for my surgery. As soon as I received the money, I was arrested and charged with extortion."
She spent about a month in jail.
She now spends much of her time fighting for gender rights.
This article was first published on Nov 21, 2014. Get The New Paper for more stories.