When Floyd Mayweather Jr. took on Conor McGregor in August 2017, it was said the winner of that anticipated Las Vegas crossover fight would take home a minimum of $100 million. It should be no surprise, then, that Mayweather, who ousted his MMA-turned-boxing opponent with a 10th-round knockout, ranks first on Forbes' 2018 list of highest-paid athletes. Leapfrogging soccer stalwart Cristiano Ronaldo, the 41-year-old boxer earned an estimated $285 million in 2017 alone -- $275 million in pay and another $10 million in endorsements.

The undefeated "Money" Mayweather has been a staple of Forbes' annual ranking of rich athletes, topping the list from 2012-2014.

If the list were based on just endorsement earnings, 36-year-old tennis superstar Roger Federer would take the crown after raking in an estimated $65 million in that department in 2017. Regularly among the top earners in tennis thanks to partnerships with Nike and numerous Swiss brands, he also made an estimated $12.2 million to bring his total yearly earnings to a No. 7-ranked $77.2 million.

Besides Ronaldo, the Real Madrid and Portugal national star who brought in $61 million in pay and $47 million in endorsements for the No. 3 ranking, future NBA Hall of Famer LeBron James may have been the most well-rounded earner of 2017. The 33-year-old Cleveland Cavaliers star and free agent-to-be ranks sixth on Forbes' 2018 list but had a relatively even split between salary ($33.5M) and endorsements ($52M), for which he has been known since coming out of high school.

Soccer's Lionel Messi ranked second on the list, while McGregor (4) and Paris Saint-Germain's Neymar (5) rounded out the top five. 

Also notable: No female athletes cracked the top 100, with Serena Williams just missing out with an estimated $18 million in earnings. Williams has been on previous editions of the list, as well as rival Maria Sharapova, who was Forbes' highest-paid female athlete for 11 years straight, starting in 2004, until Serena finally unseated her in 2016.

The NFL makes its first appearance on the ranking at No. 9, where Atlanta Falcons quarterback Matt Ryan is said to have earned $67.3 million in 2017. Auto racing first appears at No. 12 with Lewis Hamilton ($51 million), golf gets its first representative with Tiger Woods ($43.3 million) at No. 16, and baseball doesn't show up until No. 37 with Los Angeles Dodgers pitcher Clayton Kershaw ($34.5 million).

Here's the full rundown of the top 10 highest-paid athletes, according to Forbes' estimates:

  1. Floyd Mayweather Jr. ($285 million)
  2.  Lionel Messi ($111 million)
  3.  Cristiano Ronaldo ($108 million)
  4.  Conor McGregor ($99 million)
  5.  Neymar ($90 million)
  6.  LeBron James ($85.5 million)
  7.  Roger Federer ($77.2 million)
  8.  Stephen Curry ($76.9 million)
  9.  Matt Ryan ($67.3 million)
  10.  Matthew Stafford ($59.5 million)