The Swiss maestro jumped four spots to sit top of the pile, earning $106.3million in the past year as he becomes the first tennis player to lead the way.
That eye-watering figure puts the 20-time grand slam winner ahead of football stars Ronaldo ($105m), Messi ($104m) and Neymar ($95.5m).
Endorsements account for most of Federer's income, but he also undertook a tour of North and South America late last year to further boost his earnings.
"The coronavirus pandemic triggered salary cuts for soccer stars Messi and Ronaldo, clearing the way for a tennis player to rank as the world's highest-paid athlete for the first time," said Kurt Badenhausen, senior editor at Forbes.
"Roger Federer is the perfect pitchman for companies, resulting in an unparalleled endorsement portfolio of blue-chip brands worth $100million a year for the tennis great."
Federer's rise to the summit comes after fellow tennis player Naomi Osaka was announced as the highest-paid female athlete, her $37.4m putting the Japanese 29th overall.