President Emmanuel Macron on Friday bestowed France's highest order of merit on the pioneering US tennis great Billie Jean King, as she celebrates the 50th anniversary of her French Open victory.

"In 50 years you have revolutionised international sport, but also equality between women and men and the rights of minorities worldwide," Macron said at the Elysee Palace ceremony.

"Your history is an American dream, one of these destinies that are almost too good to be true," he said.

King, who is attending this year's French Open at Roland Garros, was also honoured by the tournament organisers Thursday with a video of fellow legends saluting her title win at the 1972 tournament.

The following year she made history by dominating Bobby Riggs in the "Battle of the Sexes" exhibition match, a key moment as the push for women's rights gained ground.

King was also among the Original Nine female players who defied tennis authorities by creating their own women's circuit to denounce the huge discrepancy in prize money and competition opportunities compared to men.

That led the US open to start offering the same prize money to  women as men in 1973, and paved the way for a wave of wealthy female superstars such as Serena Williams and Maria Sharapova.

And in 1981, she withstood a fierce backlash after being outed as a lesbian and acknowledging her sexuality, a groundbreaking -- and risky -- stance for an international sports star.

"It was a very difficult moment, but I told the truth. And the next day I lost all my sponsors," she told French television this week.

"I want to thank you for everything you've done for women's tennis and for women," Martina Navratilova said in the French Open video.

"What a beautiful tribute. Thank you," King responded in a tweet.