Not a single woman has been included among the world's top 100 earning sportspeople - the first time it has been entirely populated by men since Forbes began compiling an extended list eight years ago.
Mayweather, Ronaldo and Tiger Woods are the only three athletes to have topped the list over the past 18 years, Forbes said.
Forbes estimated that in the last 12 months as of June 1, she earned $18 million, which put her below the 100th athlete on the 2018 list ― National Basketball Association player Nicolas Batum, who earned $22.9 million.
However, the victor of 23 single grand slam titles has only just returned to action after giving birth to her daughter Alexis nine months ago and, while her endorsements stood at $18 million, it was not enough to remain in the list.
The American's earnings from the McGregor fight made him the world's best paid for the fourth time in seven years, with $US285 million ($374 million).More news: Chelsea star Willian rates new Man Utd signing Fred
NBA's top earner LeBron James banked $85.5 million, including endorsements, over the last 12 months to rank sixth among the highest-paid athletes.
Messi's annual salary, including bonus payments, is said to be $84 million (R1.07 billion) following his latest contract extension, while he also earned an extra $27 million (R343 million) from endorsement deals with the likes of adidas, Gatorade, Pepsi and Huawei to take his overall income to $111 million (R1.41 billion).
Brazil and Paris St Germain star Neymar joins Messi and Ronaldo in the top five.
NBA stars lead with a record-topping 40 basketball players among the top 100.
American golfer Phil Mickelson (47) was the oldest athlete in the top 100 with earnings of $41.3m while Greek basketballer Giannis Antetokounmpo (23) was the youngest with earnings of $35.5m. There are 22 different countries represented in the top 100. However, that was about $5 million less than National Basketball Association player Nicolas Batum, who landed the 100th spot on the list.