The 23-time grand slam champion made the list behind big endorsements, including Nike, JPMorgan Chase and Gatorade, investing in startups – Williams has put money into 34 over the past five years – and her recently launched company, Serena Ventures, which focuses on companies founded by women and minorities.
Forbes released the list on Wednesday (AEST) which also featured Oprah Winfrey (number 10), Rihanna (37), Vera Wang (45) and Ellen DeGeneres (63), among many others.
Williams, 30, ranked 80th overall with an estimated fortune of $225million.
"It's fun to get in there. I don't gamble. I don't jump off buildings," she told Forbes. "I'm the most non-taking-a-chance kind of a person, but I felt like seed [investing] was where we wanted to be."
Forbes noted Williams' $29m total income over the past 12 months is the highest of her career.
"I want to be a part of it," Williams said. "I want to be in the infrastructure. I want to be the brand, instead of just being the face."
Williams made it clear, however, she will continue playing tennis at the highest level.
The American suffered a third-round loss at the French Open, leaving her one short of matching Margaret Court's all-time record of 24 grand slams.
"I am in no rush to get out of this sport," Williams said. "I want to create a brand that has longevity, kind of like my career. It's not fancy, it's not here, it's not out, it's not trendy, it's a staple, like my tennis game."