The video appeared less than three weeks after her U.S. Open final defeat to Naomi Osaka, where an umpire treated her with obvious sexism.
In the Instagram video, Williams covers her breasts with her hands while singing a version of Australian band The Divinyls' 1991 hit in support of Breast Cancer Network Australia.
"This Breast Cancer Awareness Month I've recorded a version of The Divinyls global hit 'I Touch Myself' to remind women to self-check regularly," wrote Williams on the post. "Yes, this put me out of my comfort zone, but I wanted to do it because it's an issue that affects all women of all colors, all around the world. Early detection is key — it saves so many lives."
The song was co-written by Divinyls Australian vocalist Chrissy Amphlett who died of breast cancer five years ago aged 53.
"The music video is part of the I Touch Myself Project which was created in honor of celebrated diva, Chrissy Amphlett, who passed away from breast cancer, and who gave us her hit song to remind women to put their health first," said the 23-time Grand Slam champion.
The video was viewed more than 1.3 million times in the first 10 hours after it was posted early Sunday with fans lauding the tennis superstar for her bravery in performing the song.
"Amazing Serena, important message and such a beautiful voice!" wrote one under the username deedpaula. Another alshaze47 commented: "This is powerful!! I'm a Breast cancer survivor!!"
Williams, who celebrated her 37th birthday four days ago, pulled out of this week's China Open in Beijing to bring a premature end to her 2018 season, her first back on tour since giving birth to a daughter a year ago.
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