In a wide-ranging interview with Vogue magazine, the 35-year-old American said she planned to return to the sport just months after giving birth and spoke about how her race has shaped the way she is perceived by some people.
Williams, a 23-time grand slam champion, said she was seen as "mean" and "tough" by some because she was black, adding that she had to be twice as good as blonde Russian Maria Sharapova, winner of five grand slam titles, to gain the affection of the wider public.
"I feel like people think I'm mean," Williams told Vogue.
"Really tough and really mean and really street.
"I believe that the other girls in the locker room will say, 'Serena's really nice.' But Maria Sharapova, who might not talk to anybody, might be perceived by the public as nicer.
"Why is that? Because I'm black and so I look mean? That's the society we live in. That's life. They say African-Americans have to be twice as good, especially women. I'm perfectly OK with having to be twice as good."
Wanting to be an inspiration
This is the third time Williams has appeared on the cover of Vogue, having previously done so in June 2012 and April 2015. Last month, the mum-to-be posed nude for the cover of Vanity Fair.
She said she did so because she wanted to be a role model for other black girls.
"The success of one woman should be the inspiration to another, and I'm always trying to inspire and motivate the black girls out there," said Williams, who is expecting her first child with fiance, the Reddit co-founder, Alexis Ohanian.
"I'm not a model. I'm not the girl next door. But I'm not hiding.
"Actually, I look like a lot of women out there. The American woman is many women, and I think it's important to speak to American women at a time when they need encouragement. I'm not political, but I think everyone is worried, to a degree."
'Either I win or I don't play'
Williams, who is deep into her third trimester, is the most successful tennis player in the open era having overtaken Steffi Graf's record haul by winning the Australian Open in January, a feat achieved while pregnant.
She has not played since her historic triumph in Melbourne, but Williams has set her sights on returning for the first grand slam of 2018, which starts on January 15.
And another title in Australia would see her equal Margaret Court's all-time singles record of 24 grand slams.
"It's the most outrageous plan," she admitted. "I just want to put that out there. That's, like, three months after I give birth. I'm not walking anything back, but I'm just saying it's pretty intense.
"In this game you can go dark fast. If I lose, and I lose again, it's like, she's done. Especially since I'm not 20 years old. I'll tell you this much: I won't win less. Either I win, or I don't play."
Williams, widely regarded as the best server of all time in the women's game, also spoke of a "love-hate relationship with the idea of power," in the interview.
"Not only me, but women in general sometimes feel that power is a bad word," she said.
"As I've gotten older I've started to feel differently about it. Power is beauty. Strength is beauty. So now on the court I want people to think that I'm powerful.
"But I also want them to be shocked at how I play. I want people to expect something, then get something different."