"The cycles of poverty, discrimination, and sexism are much, much harder to break than the record for Grand Slam titles," said Williams, decrying statistics showing "women of color have to work on average eight months longer to earn the same as their male counterparts do in one year."
"For every black woman that rises through the ranks to a position of power, there are too many others who are still struggling."
She has previously been forced to defend how much female players receive at Grand Slam tournaments, despite Wimbledon only instituting equal pay for singles winners in 2007.
"In every stage of my life, I've had to learn to stand up for myself and speak out," said Williams, who is currently taking time out of the game to give birth to her first child.
"I have been treated unfairly, I've been disrespected by my male colleagues and—in the most painful times—I've been the subject of racist remarks on and off the tennis court."
"I don't think any woman should be down on their knees thanking anybody like that," Williams told reporters. "I don't think that is a very accurate statement."
This latest essay speaks to a far wider disparity - one she argues is as prevalent "in inner cities as it is in Silicon Valley."
"Today isn't about me," writes Williams. "It's about the other 24 million black women in America. If I never picked up a tennis racket, I would be one of them; that is never lost on me."
"Black women: Be fearless. Speak out for