According to the publication, the 23-time Grand Slam champion made the list as a result of her estimated fortune of $224m (£177m).
The majority of William's fortune has been made as a result of her “brain and brand rather than her backhand”, according to Forbes, with the star investing in 34 startup business in the past five years alone.
Opening up about her financial investments, Williams told the publication: “I want to be in the infrastructure. I want to be the brand, instead of just being the face.”
In April, Williams announced she was launching her own venture-capital firm, Serena Ventures, in a post on Instagram.
In the announcement, the tennis star revealed she had launched the firm “with the mission of giving opportunities to founders across an array of industries” and that the company has been quietly investing in more than 30 companies since 2014.
Forbes reports that 60 per cent of Williams’ investments so far have gone to companies led by women or people of colour.
“What better way to preach that message?” Williams told the magazine.
On the prospect of whether she’d turn her back on tennis for good in favour of a career in finance, the mother-of-one added: “I am in no rush to get out of this sport.
“I want to create a brand that has longevity, kind of like my career,” she continued.
“It’s not fancy, it’s not here, it’s not out, it’s not trendy, it’s a staple, like my tennis game.”
Williams said she has openly been seeking the support of her husband, Alexis Ohanian, who is co-founder and executive chairman of the social news aggregator website Reddit.
“I’ve been really leaning on Alexis,” Williams admitted, with Ohanian describing his wife as being “determined to be great at everything she does”.
Williams’ Forbes accolade comes days after she lost to American Sofia Kenin in the third round of the French Open.
On Sunday, the 37-year-old reflected on her defeat, telling her 11m followers that she was looking to the future.
“Yesterday was not my day. But it’s about getting up time and time again after you fall,” Williams wrote in the caption to a photo of her during the match. “Here’s to a multitude of tomorrows.”
Several celebrities commented on the post to offer their support to the athlete.
“You got it mama,” wrote singer Ciara.
Tom Brady, the New England Patriots quarterback, added: “You got that right”
“Yes!,” former tennis champion Billie Jean King added.
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