Serena Williams plays a forehand during Wimbledon. (Photo: Andy Cheung / Getty Images) 
There will never be consensus about the greatest athletes of all time in one sport, let alone across all sports. Team performers are different from individual sports stars, but they share the common trait of elevating their professions to unthought-of heights. The elite also transcend sport because of their increasingly crucial roles in social justice causes.
With that in mind, we present the five greatest female athletes of the 21st century.
Serena Williams (Tennis)
Serena Williams is a polarising figure, adored by many and disliked by some, for her apparent penchant for petulance when things don’t pan out as she would like.
However, even her detractors would be found wanting were they to argue against her being not only one of the greatest female athletes of all time, but one of the greatest athletes of all time, period.
Her victories have moulded her into an inspirational figure in the sport of tennis, especially to children. Last year Williams opened up about the struggles she has faced throughout her career, including discrimination.
“In short, it’s never been easy,” Williams wrote in an essay published in Harper’s Bazaar. “But then I think of the next girl who is going to come along who looks like me, and I hope, maybe, just maybe, my voice will help her.”
The 38-year-old has racked up an impressive catalogue of achievements, including 23 Grand Slam singles titles, 14 Grand Slam doubles titles with sister Venus, and four Olympic gold medals.
Williams has been ranked the number one player in the world on eight separate occasions. During her sixth reign on top, she held the ranking for 186 consecutive weeks, which tied Steffi Graf for longest all-time.
Serena and Venus Williams are considered pioneers of a new era for women in tennis that is focused on power. In 2019, she was the only woman on the list of the world's highest-paid athletes, according to Forbes.
Serena Williams has also won the Laureus World Sportswoman of the Year a record four times.
width="853" height="480" frameborder="0" allowfullscreen="allowfullscreen">
Caster Semenya (Athletics)
/file/dailymaverick/wp-content/uploads/Craig-yanga-top-five-caster-semenya.jpg "Caster Semenya. (Photo: Roger Sedres / Gallo Images)")
There might not be a more controversial athlete on the planet than Semenya – through no fault of her own. The multiple Olympic and world 800m champion has been the subject of debate, ridicule, racism and sexism. Through it all, she has maintained her dignity as her gender identity has been a subject of heated debate. She identifies as female, but her naturally elevated testosterone levels have been a source of controversy.
Semenya is an Olympic and World Championship gold medal winner over 800m, which is rare in itself. But having achieved the success she has, under the scrutiny she has had to endure, elevates her into a rare category of athlete.
After winning the 2009 World Championship 800m title, she was subjected to “sex verification testing” by the IAAF. This was done after she improved her best times by massive margins that year. It led to a public outcry and eventually Semenya was allowed to compete the following year.
She won the 800m at the 2011 World Championships and 2012 Olympics after Russian winner Mariya Savinova was retrospectively disqualified after failing doping tests. Semenya also claimed the 2016 Olympic gold and 2017 World Championship gold before the IAAF intervened again.
In a landmark case at the Court of Arbitration for Sport (CAS), the IAAF won a case to compel athletes such as Semenya with differences in sexual development (DSDs) to take medication to reduce their natural testosterone levels.
Athletes with testosterone levels higher than five nmol/litre would not be eligible to run distances from 400m to one mile (1600m). If they took the medication and reduced their testosterone to below that level for a period of six months, they would be eligible again.
The CAS tribunal panel’s ruling came with several caveats, including that it found the IAAF’s policy to be “discriminatory” but that it was a “necessary, reasonable and proportionate means of achieving the IAAF’s aim of preserving the integrity of female athletics in the restricted events”.
Semenya refused to take the medication, for several reasons, not least of which might be harmful side-effects. She has opted to rather focus on events such as the 200m, which do not fall into the penalised distances.
“I know that the IAAF’s regulations have always targeted me specifically,” Semenya said after the 2019 CAS ruling. “For a decade the IAAF has tried to slow me down, but this has actually made me stronger. The decision of the CAS will not hold me back. I will once again rise above and continue to inspire young women and athletes in South Africa and around the world.”
/file/dailymaverick/wp-content/uploads/Craig-yanga-top-five-inset-Megan-Rapinoe.jpg "Megan Rapinoe of the United States. (Photo: Ronald Martinez / Getty Images)")
/file/dailymaverick/wp-content/uploads/Craig-yanga-top-five-inset-Annika-Sorenstam.jpg "Annika Sorenstam of Sweden. (Photo: Kevin C Cox / Getty Images)")
/file/dailymaverick/wp-content/uploads/Craig-yanga-top-five-inset-Simone-Biles.jpg "Simone Biles of the US. (Photo: Laurence Griffiths / Getty Images)")