Serena Williams is widely regarded as the best tennis player to ever grace the court. Her sporting success has made her a household name but her business ventures are just as fascinating. In fact, her decorated career and impressive business partnerships could see her become the world's first ever female athlete billionaire.That's according to Andrew Petcash, founder of sports business newsletter Petcash Post, who has highlighted how Williams' investment portfolio could see her already handsome net worth skyrocket in the coming years.The queen of the court is the highest paid female athlete of all time and it's easy to see why.With a total of 39 Grand Slam titles (23 singles, 14 doubles, two mixed doubles) and four Olympic gold medals, Williams has reportedly earned upwards of $94 million from tennis tournaments across her glittering career. Petcash also reports the 40-year-old makes more than $15 million a year through endorsements alone. Williams has signed a number of lucrative deals over the years with huge brands including Nike, Pepsi, and Beats by Dre. As the most successful female singles player of the Open Era, the US star is extremely marketable. Williams currently has a net worth of $225 million, which Petcash has predicted to rise significantly based on her investments.

Serena Williams investments

Her venture capital firm, Serena Ventures, recently raised a staggering $111 million in an inaugural fund and has invested in more than 50 startup companies since being founded in 2014.

Williams originally backed some 60 companies as an angel investor — an individual who uses their own funds to support a start-up company or project. From there, she built Serena Ventures to expand her efforts and continue to provide opportunities for others.

"As an angel investor, you can only do so much," she recently told Black Enterprise. "I knew that I wanted to do a fund, but I worked backward, by using my own capital and then creating a track record and getting to know everyone."

Serena Ventures works to change the landscape of venture capital. After discovering less than two percent of all VC money goes to women, the former world number one was stunned and knew she had to try to make a difference.

"I wanted to really bring diversity to VC in the way that I could. And the only way to change those numbers was to be the person writing the big checks."

Serena Ventures' portfolio features a healthy 76 percent majority of companies led by individuals from under-represented backgrounds, including women (53 percent) and Black business owners (47 percent).

MELBOURNE, AUSTRALIA - JANUARY 28: Serena Williams of the United States poses with the Daphne Akhurst Trophy after winning the Women's Singles Final against Venus Williams of the United States on day 13 of the 2017 Australian Open at Melbourne Park on January 28, 2017 in Melbourne, Australia. (Photo by Clive Brunskill/Getty Images)

Serena Williams of the United States poses with the Daphne Akhurst Trophy after winning the Women's Singles Final against Venus Williams of the United States on day 13 of the 2017 Australian Open at Melbourne Park on January 28, 2017 in Melbourne, Australia. (Photo by Clive Brunskill/Getty Images)

Stakes in big companies

Williams also has stakes in larger companies and sporting organisations, which in some cases have soared in valuation since she started her investment.

Petcash reports Williams invested in the UFC in 2016, which has climbed from a $5 billion valuation to more than $10 billion.

She also has a stake in fitness company Tonal, along with fellow athletes including LeBron James and Mike Tyson. Since investing in 2019, Tonal has risen from a $45 million valuation to beyond $1.6 billion.

Williams and her sister Venus both acquired a minority stake in NFL team the Miami Dolphins back in 2009, which has since spiked from $1 billion to $3.4 billion in valuation.

As well as being an incredible athlete and businesswoman, Williams is a philanthropist who has helped build schools for children in African and the Caribbean, raised $65,000 for Kaikoura earthquake recovery, and started up the Serena Williams Fund.