Billie Jean King was unmasked as Royal Hen on the latest episode of The Masked Singer US, Season 10.

The show consists of several celebrities from various fields singing while concealed by an elaborate mask. Meanwhile, the panel of judges must guess who is behind each one, with a celebrity being eliminated (and consequently unmasked) at the end of each week's episode.

In the most recent broadcast, King - under the alias of "Royal Hen"- took part in "A Celebration of Elton John", performing "Philadelphia Freedom." Each masked celebrity also has an intro where they give some further hints as to their identity, with King's alluding to her successful career and huge impact on the sport.

King was an advocate for gender equality throughout her tennis career and remains so to this day. She secured equal prize money at the 1973 US Open, founded the WTA, and defeated Bobby Riggs in the Battle of the Sexes, which had a huge social impact.

"We welcome viewers to the coronation of the Royal Hen. For the first time ever, the Royal Hen is set to hold court. A true trail blazer, she is famous for championing equal opportunities for all, and has made it her royal mission to be a voice for the voiceless. Her road to stardom was wrought with prejudice. She knew sitting idly by was for the birds. She was no chicken.

"She entered the ring bravely and proved to her 90 million subjects that she was worthy of the crown. Here she is receiving the royal stadium hot dog. Now, having inspired a new flock of birds, her name is etched in history. Congratulations, we are here to serve you. God save the Royal Hen," the intro read.

Nevertheless, it was only panelist Ken Jeong who guessed the 79-year-old's identity correctly, while Rita Moreno, Gloria Steinem, and Dr Ruth were the other guesses put forward by judges Jenny McCarthy Wahlberg, Robin Thicke, and Nicole Scherzinger.

At the end of the episode, King lost to Hawk in the sing-offs and thus revealed her identity, at which point the crowd went wild.

"We have an icon in the building!" declared host Nick Cannon as King smiled at the crowd and the judges.

"You guys are so awesome. Thank you so much," she said.