The 41-year-old American's earnings from last year's fight with Irishman Conor McGregor made him the world's best paid for the fourth time in seven years, with A$374 million.
Boxing champ Floyd Mayweather and football legend Lionel Messi head the charts in the list of the world's highest-paid athletes according to Forbes. Lionel Messi clocked in at $111 million while Ronaldo followed at $108 million.
He earned a $275m (£205m) payday for his boxing match in August against UFC star Conor McGregor, who is number four on the USA business magazine's list.More news: B.C. judge expands pipeline injunction as protesters use 'calculated' defiance
Forbes said tennis' female sportspersons Li Na, Maria Sharapova and Serena Williams were list regulars but Li retired in 2014 and Sharapova is still dealing with the aftermath of a 15-month suspension for using a banned substance.
Lionel Messi was named the second highest earner with pay of $111m (£83.1m) previous year, with his great rival Cristiano Ronaldo earning slightly less in 2018 with $108m (£80.9m).
The "World's Highest-Paid Athletes 2018" list is topped by 41-year-old Mayweather, with Dollars 285 million earnings. NBA stars lead the way with 40 basketball players among the top 100.More news: ASUS announces new ZenBook, VivoBook notebooks, and VivoWatch BP healthcare wearable
F1 driver Lewis Hamilton is the top Briton at number 12 with $51m. Apart from the aforementioned trio, no Indians have featured in the richest list.
According to the 2017 top earning list of Australian athletes, former world number one golfer Jason Day would be the closest to cracking the list, having earned AU$18.9m a year ago.
This year 40 National Basketball Association players made the cut in Forbes' annual look at the world's 100 highest-paid athletes, breaking the record of 32 set last year by hoopsters.More news: 'Mission Impossible - Fallout' Featurette Details Tom Cruise's Harrowing 25000-Foot HALO Jump
Endorsement income from sponsorship deals fell slightly, by 1% to $877m. Basketball players in particular make money from both sports and the products they endorse.