Serena Williams is using her public platform -- and her baby bump! -- to advocate for equal pay.
The tennis pro took to Instagram on Monday -- rocking a grey shirt with the words "Phenomenal Woman" that showed off her growing bump -- to speak out about the financial discrepancy black women face in the workplace.
"July 31 is Black Women's Equal Pay Day, which represents the number of days into 2017 a black woman must work to earn the same pay a white man made in 2016 -- that's nearly 8 extra months!" Williams wrote in the caption. "Black women are the cornerstone of our communities, they are phenomenal, and they deserve equal pay."
WATCH: Serena Williams Shows Off Baby Bump, Slays in Fitted Gray Dress
Williams, who is currently expecting her first child with fiancé Alexis Ohanian, also shared a post promoting her upcoming interview with Fortune Magazine, in which she elaborates on her efforts to combat the wage gap.
"The gender pay gap hits woman of color the hardest," she wrote. "I hope I can give a voice to those who aren't heard."
WATCH: Serena Williams and Fiance Alexis Ohanian Take 'Baby Class 101' -- See Their Swaddles!
When she's not combating institutional sexism in the American workplace, the mom-to-be is making sure to shut down the sexism she faces in her personal life -- like when she spoke out against John McEnroe last month, after he said that, if Williams played on the men's circuit, she'd be ranked "like No. 700 in the world."
"Dear John, I adore and respect you but please, please keep me out of your statements that are not factually based," Williams, 35, wrote in a series of tweets. "I've never played anyone ranked 'there' nor do I have time. Respect me and my privacy as I'm trying to have a baby. Good day sir."
Check out the video below to hear more about the tennis stars' volley of pointed comments.