Martina Navratilova wants Billie Jean King to explain her support for transgender athletes

Martina Navratilova is calling “foul" on her longtime friend, Billie Jean King, over the issue of transgender women’s participation in women’s sports. The two lesbian icons, who faced each other 16 times in their professional careers, have both blazed trails for human rights and supported women’s causes in sports and society. But this topic has divided them for more than five years.

Their dispute began when Navratilova tweeted in 2018 that “You can’t just proclaim yourself a female and be able to compete against women," which she swiftly deleted upon being labeled transphobic. In 2020, King joined lesbian soccer icon Megan Rapinoe, queer WNBA legend Candace Parker, and the Women's Sports Foundation in declaring their support for the inclusion of trans girls in sports.

Now, in an interview with OutKick, a sports and political commentary site owned by Fox Corporation, one of the tennis legends challenged the other to defend her support for transgender women athletes in light of King's other public comments about physical differences between men and women.

Related: Martina Navratilova Tells Daniel Radcliffe to 'Be Quiet' on Supporting Transgender Rights

"I think she thinks that they play fair and square, meaning males identify as women, take all the hormones and do everything, like Renée Richards did 50 years ago," Navratilova told Outkick. "And that it’s just nice to include everybody."

As recently as April, King publicly acknowledged physical differences between men and women.

"The girls have never said we're better than the guys," she said. "The guys are better, by the way. They're stronger, they have a better skeletal system, their hearts are bigger. We've never said we're better than the men or as good even."

King made those comments while speaking at the Center for Public Leadership at Harvard Kennedy School, where she accepted the 2026 Gleitsman Citizen Activist Award. Her remarks came during a discussion of the famous "Battle of the Sexes" match, when she defeated former world number one Bobby Riggs in 1973. As The Advocate previously reported, that match was dramatized in the 2017 film Battle of the Sexes, starring Emma Stone as King and Steve Carell as Riggs.

That video of King talking about the differences between men and women was edited and re-posted on social media last month by XX-XY Athletics, the for-profit sportswear company that doubles as an anti-trans inclusion advocacy corporation. Its founder and CEO is former gymnastics champion and anti-trans activist Jennifer Sey. Last year, Sey offered $35,000 to any National Women's Soccer League player willing to publicly oppose the participation of transgender and intersex athletes. As Out reported at the time, no player accepted the offer.

The edited video intersperses comments from cisgender female student-athletes, including: "So why do you support males in women's sports, Billie Jean?" The video asks King to "make it make sense."

Related: Martina Navratilova and J.K. Rowling are attacking the U.N. for being trans-inclusive

"The solution is obvious," Navratilova told OutKick. "No male bodies in women’s sports and no male bodies in women's sex-based spaces for many different reasons, not the least of which is women’s rights to safety, dignity and fairness and privacy."

Navratilova also referenced comments King made to The Advocate in 2024 about their private conversations on the issue, saying those discussions have made King's public position more frustrating to her.

"Billie Jean has repeatedly told me over the last four or five years that she would love to talk to me about it, that she defers to me because I know a lot more about it than she does," Navratilova said.

But Navratilova said the conversations she expected never really happened.

"Without talking to me really and listening to what my points were, she just went her way and put out the statement by her and the Women’s Sports Foundation about inclusion and all this stuff," Navratilova said. "I don’t think she really has heard the other side of the debate, so to speak," she claimed.

But that’s not what King told The Advocate. The out lesbian icon was posing for selfies with fans following her appearance at the September 2024 Lesbians Who Tech Summit in New York City, when she was asked if she would talk with Martina Navratilova about supporting trans women.

"We talk. We talk," she said. "I tell her our relationship is the most important thing, and let's talk."

In a 2025 interview with The Telegraph ahead of Wimbledon, King called the broader transgender-athlete debate in sports "a nightmare" and said people should listen to transgender people’s stories and make them feel included, as The Advocate reported.

But Navratilova told Outkick she wants King to answer the question directly: how does she square her position about the physical differences between men and women and her support for trans female athletes?

"I honestly don’t know because it doesn’t square," Navratilova said. "Please get Billie Jean on record," she added. "I’d like to know how she explains it because she hasn’t been able to explain it to me."

The Advocate reached out to King’s representative as well as the Women’s Sports Foundation for comment, and did not hear back.